feat: add file-based admin settings panel at /admin (#866)

* feat: add file-based admin settings panel at /admin

Settings saved in the panel are written to data/settings.json and
overlaid onto process.env, taking precedence over environment
variables and applying immediately without restart. Enable by setting
ADMIN_PASSWORD; on serverless platforms without persistent disk the
panel degrades to read-only.

* polish: admin panel UI improvements

- Provider logos in credential rows (shared ProviderLogo component,
  extracted from model-config-dialog)
- Scroll-spy active state in the sidebar nav
- Green success state in the save bar that clears after a few seconds
- Wider content column (max-w-6xl) for less wasted space on desktop

* polish: admin panel section toggles and reorder

- Move Quota & Rate Limits to the end of the settings page
- Add enable switches to Observability and Quota sections; default off
  with fields grayed out, auto-on when any field is already configured

* polish: make section enable switch more visible

Wrap the switch in a labeled pill ('Enabled'/'Disabled') with border
and background so the off state is clearly visible.

* refactor: derive admin registry from PROVIDER_INFO, simplify page state

- Provider options, labels, and base-URL placeholders now come from
  PROVIDER_INFO instead of hand-copied lists (fixes SiliconFlow .com/.cn
  placeholder drift; panel names now match the model-config dialog)
- Replace free-text subgroup strings + SUBGROUP_PROVIDERS reverse map
  with a typed provider field on SettingDef
- Precompute SETTINGS_BY_GROUP and PROVIDER_SUBGROUPS at module level
- Merge justSaved into saveMessage, drop unused mainRef, hoist
  fetchSettings out of the component, dedupe savedText logic
- Serialize from SETTINGS_REGISTRY directly; json validators in a map
  instead of a hardcoded key check
- Make allowPrivateUrls a function so ALLOW_PRIVATE_URLS edits in the
  admin panel apply without restart

* feat: graphical model management in admin panel

Replace the provider credential fields and raw AI_MODELS_CONFIG JSON
textarea with a Models section mirroring the in-app model settings UI:
provider instance list with logos, credential fields per provider type,
model add/remove with suggestions, per-model connectivity test, and a
default-provider star.

On save the server derives everything the runtime needs into
settings.json: credential env vars (with _2 suffixes for multiple
instances of one provider), AI_MODELS_CONFIG, and AI_PROVIDER/AI_MODEL
for the default. Secrets round-trip as masked markers and are never
sent back to the browser. The general settings registry now only
covers non-provider settings (generation, access, features,
observability, quota).

* fix: allow testing unsaved providers in admin panel

The test button previously looked up credentials by providerId in the
saved settings, so testing a newly added (unsaved) provider failed with
'Unknown provider or model'. The test endpoint now accepts the client's
current provider state; newly typed secrets are used as-is and masked
markers are resolved against the stored values, so testing works both
before and after saving.

* fix: merge env AI_MODELS_CONFIG with admin panel providers

Previously, saving in the admin panel wrote a complete AI_MODELS_CONFIG
into settings.json, which (by overlay precedence) replaced any config
from .env or ai-models.json — admins lost their env-configured models.

The panel no longer writes AI_MODELS_CONFIG. Instead its providers are
merged with the env baseline at read time in loadRawServerModelsConfig,
and panel credentials go to ADMIN_-prefixed env vars wired up via
apiKeyEnv/baseUrlEnv so they never shadow standard vars. Env-based
providers now appear read-only in the panel, name clashes are rejected,
and a panel default overrides the env default. data/ is now gitignored.

* fix: block global-credential providers already managed via env

Bedrock, Vertex AI, and Ollama credentials live in fixed env vars with
no apiKeyEnv redirection, so a panel instance of one of these would
silently override the credentials that env-configured models rely on.
The API now rejects saving such a provider when the env config already
uses that type, and the Add Provider dropdown disables it with a
'managed via env' note.

* fix: address admin panel review findings

- Security: test-model no longer resolves a stored secret when the
  request's baseUrl/provider differs from the stored entry, closing a
  path where a tampered baseUrl could exfiltrate a saved key
- Save failures are now visible: the save bar shows the error in red
  (was masked by the persistent 'Unsaved changes' text), and per-field
  validation errors from the settings API are surfaced under each field
- The Observability/Quota enable switch is now real: toggling off stages
  deletion of the group's saved values, and the toggle no longer snaps
  back to Enabled after saving
- Env provider's default star is hidden when a panel provider is the
  active default (no more double star)
- Clearing a credential field reverts to the stored value instead of
  silently deleting it; an explicit X button removes a stored secret
- Form inputs are disabled during an in-flight save

* refactor(admin): split 1549-line admin page into focused modules

Extract admin-shared.ts (types + fetch helper), setting-field.tsx
(registry-driven fields), and models-section.tsx (provider/model
manager) from page.tsx. Pure mechanical move, no behavior change.

* feat(admin): share credential fields with user dialog and localize panel

Extract ProviderCredentialsFields (display name + per-provider
credential inputs) used by both the user ModelConfigDialog and the
admin Models panel; secret input passed via renderSecret (plaintext
vs masked), test button via footer slot. Add full i18n for the admin
panel across en/zh/ja/zh-Hant, reusing modelConfig.* for shared parts.

* fix(admin): address Copilot review findings

- Reflect built-in defaults for boolean settings (ALLOW_PRIVATE_URLS
  defaults on) and allow clearing a saved boolean back to default,
  so the SSRF toggle matches actual runtime behavior.
- Harden JSON loading: filter settings values to strings only, and
  schema-validate stored ADMIN_PROVIDERS entries, dropping malformed
  ones instead of letting them reach runtime code.
- Set beforeunload returnValue so the unsaved-changes prompt shows in
  all browsers; reject non-finite numbers in settings validation.
- Fix README/CN/JA docs that claimed the panel auto-generates
  AI_MODELS_CONFIG (providers are merged at read time, not written).
- Add unit tests for corrupted-file value filtering and provider
  schema validation.

* docs: move admin panel details to dedicated docs/{en,cn,ja}/admin-panel.md

The READMEs now carry a short blurb + link, matching the existing
per-topic docs (docker.md, ai-providers.md, ...). Removes the ~22-line
inline section and the duplicated data/settings.json mentions.

* fix(admin): address follow-up Copilot findings on the prior fixes

- loadAdminProviders now validates against a stored-shape schema where
  secrets are plain strings, so a hand-edited ADMIN_PROVIDERS holding an
  {isSet} marker is dropped instead of later crashing maskSecret().
- loadSettings guards against array values (typeof [] === 'object'),
  which would otherwise overlay numeric keys onto process.env.
- Admin SecretInput uses the bare id so the shared component's
  <Label htmlFor> stays associated (only one ProviderDetail mounts).
- Add tests: marker-secret rejection, array-values guard, bedrock
  multi-secret round-trip.

app/api/admin/providers/route.ts

@@ -0,0 +1,89 @@
+import { checkAdminAuth } from "@/lib/admin/auth"
+import {
+    AdminProvidersSchema,
+    deriveEnvUpdates,
+    loadAdminProviders,
+    maskAdminProviders,
+    mergeSecrets,
+    validateAdminProviders,
+} from "@/lib/admin/providers"
+import { isSettingsWritable, saveSettings } from "@/lib/admin/settings"
+import { loadEnvServerModelsConfig } from "@/lib/server-model-config"
+
+export const runtime = "nodejs"
+export const dynamic = "force-dynamic"
+
+async function payload() {
+    // Env-based providers (AI_MODELS_CONFIG / ai-models.json) are shown
+    // read-only in the panel; their credentials live in the environment
+    const envConfig = await loadEnvServerModelsConfig()
+    const adminProviders = loadAdminProviders()
+    // A panel default overrides any env default (matches the merge in
+    // loadRawServerModelsConfig), so env stars must reflect that
+    const adminHasDefault = adminProviders.some(
+        (p) => p.isDefault && p.models.length > 0,
+    )
+    return {
+        writable: isSettingsWritable(),
+        providers: maskAdminProviders(adminProviders),
+        envProviders:
+            envConfig?.providers.map((p) => ({
+                name: p.name,
+                provider: p.provider,
+                models: p.models,
+                isDefault: !!p.default && !adminHasDefault,
+            })) ?? [],
+    }
+}
+
+export async function GET(req: Request) {
+    const authError = checkAdminAuth(req)
+    if (authError) return authError
+    return Response.json(await payload())
+}
+
+export async function PUT(req: Request) {
+    const authError = checkAdminAuth(req)
+    if (authError) return authError
+
+    if (!isSettingsWritable()) {
+        return Response.json(
+            {
+                error: "Settings file is not writable on this deployment. Configure via environment variables instead.",
+            },
+            { status: 503 },
+        )
+    }
+
+    let body: unknown
+    try {
+        body = await req.json()
+    } catch {
+        return Response.json({ error: "Invalid JSON body" }, { status: 400 })
+    }
+
+    const parsed = AdminProvidersSchema.safeParse(
+        (body as { providers?: unknown })?.providers,
+    )
+    if (!parsed.success) {
+        return Response.json(
+            {
+                error: `Invalid providers: ${parsed.error.issues[0]?.message ?? "schema mismatch"}`,
+            },
+            { status: 400 },
+        )
+    }
+
+    const stored = loadAdminProviders()
+    const merged = mergeSecrets(parsed.data, stored)
+
+    const envConfig = await loadEnvServerModelsConfig()
+    const validationError = validateAdminProviders(merged, envConfig)
+    if (validationError) {
+        return Response.json({ error: validationError }, { status: 400 })
+    }
+
+    saveSettings(deriveEnvUpdates(merged, stored))
+
+    return Response.json(await payload())
+}

app/api/admin/settings/route.ts

@@ -0,0 +1,126 @@
+import { checkAdminAuth, maskSecret } from "@/lib/admin/auth"
+import {
+    getEnvFallback,
+    getValueSource,
+    isSettingsWritable,
+    loadSettings,
+    saveSettings,
+} from "@/lib/admin/settings"
+import {
+    SETTINGS_BY_KEY,
+    SETTINGS_REGISTRY,
+    type SettingDef,
+} from "@/lib/admin/settings-registry"
+
+export const runtime = "nodejs"
+export const dynamic = "force-dynamic"
+
+function serializeSettings() {
+    const fileValues = loadSettings()
+    return SETTINGS_REGISTRY.map((def) => {
+        const source = getValueSource(def.key)
+        const raw =
+            source === "file"
+                ? fileValues[def.key]
+                : (getEnvFallback(def.key) ?? null)
+        const value = def.type === "secret" && raw ? maskSecret(raw) : raw
+        return { key: def.key, source, value }
+    })
+}
+
+export async function GET(req: Request) {
+    const authError = checkAdminAuth(req)
+    if (authError) return authError
+
+    return Response.json({
+        writable: isSettingsWritable(),
+        settings: serializeSettings(),
+    })
+}
+
+function validateValue(def: SettingDef, value: string): string | null {
+    switch (def.type) {
+        case "number": {
+            const num = Number(value)
+            if (!Number.isFinite(num)) return "Must be a number"
+            if (def.min !== undefined && num < def.min)
+                return `Must be at least ${def.min}`
+            if (def.max !== undefined && num > def.max)
+                return `Must be at most ${def.max}`
+            return null
+        }
+        case "boolean":
+            return value === "true" || value === "false"
+                ? null
+                : 'Must be "true" or "false"'
+        case "enum":
+            return def.options?.includes(value)
+                ? null
+                : `Must be one of: ${def.options?.join(", ")}`
+        default:
+            return null
+    }
+}
+
+export async function PUT(req: Request) {
+    const authError = checkAdminAuth(req)
+    if (authError) return authError
+
+    if (!isSettingsWritable()) {
+        return Response.json(
+            {
+                error: "Settings file is not writable on this deployment. Configure via environment variables instead.",
+            },
+            { status: 503 },
+        )
+    }
+
+    let body: { values?: Record<string, unknown> }
+    try {
+        body = await req.json()
+    } catch {
+        return Response.json({ error: "Invalid JSON body" }, { status: 400 })
+    }
+    if (!body.values || typeof body.values !== "object") {
+        return Response.json(
+            { error: "Body must contain a values object" },
+            { status: 400 },
+        )
+    }
+
+    const updates: Record<string, string | null> = {}
+    const errors: Record<string, string> = {}
+
+    for (const [key, value] of Object.entries(body.values)) {
+        const def = SETTINGS_BY_KEY.get(key)
+        if (!def) {
+            errors[key] = "Unknown setting"
+            continue
+        }
+        if (value === null || value === "") {
+            updates[key] = null
+            continue
+        }
+        if (typeof value !== "string") {
+            errors[key] = "Value must be a string"
+            continue
+        }
+        const error = validateValue(def, value)
+        if (error) {
+            errors[key] = error
+            continue
+        }
+        updates[key] = value
+    }
+
+    if (Object.keys(errors).length > 0) {
+        return Response.json({ errors }, { status: 400 })
+    }
+
+    saveSettings(updates)
+
+    return Response.json({
+        writable: true,
+        settings: serializeSettings(),
+    })
+}

app/api/admin/test-model/route.ts

@@ -0,0 +1,66 @@
+import { POST as validateModel } from "@/app/api/validate-model/route"
+import { checkAdminAuth } from "@/lib/admin/auth"
+import {
+    AdminProviderSchema,
+    loadAdminProviders,
+    mergeSecrets,
+} from "@/lib/admin/providers"
+
+export const runtime = "nodejs"
+export const dynamic = "force-dynamic"
+
+// Test a model with the client's CURRENT provider state (which may be
+// unsaved). Secret fields arrive either as plaintext (newly typed) or as
+// masked {isSet} markers, which are resolved against settings.json — so
+// testing works both before and after saving.
+export async function POST(req: Request) {
+    const authError = checkAdminAuth(req)
+    if (authError) return authError
+
+    let body: { provider?: unknown; modelId?: string }
+    try {
+        body = await req.json()
+    } catch {
+        return Response.json({ error: "Invalid JSON body" }, { status: 400 })
+    }
+
+    const parsed = AdminProviderSchema.safeParse(body.provider)
+    if (!parsed.success || !body.modelId) {
+        return Response.json(
+            { valid: false, error: "Invalid provider or model" },
+            { status: 400 },
+        )
+    }
+
+    // SECURITY: a stored secret is only resolved from an {isSet} marker if
+    // the endpoint it would be sent to (provider + baseUrl) still matches
+    // the stored entry. Otherwise a tampered baseUrl could exfiltrate the
+    // stored key to an arbitrary host. Mismatches must re-supply plaintext.
+    const stored = loadAdminProviders().find((p) => p.id === parsed.data.id)
+    const sameEndpoint =
+        stored &&
+        stored.provider === parsed.data.provider &&
+        (stored.baseUrl ?? "") === (parsed.data.baseUrl ?? "") &&
+        (stored.awsRegion ?? "") === (parsed.data.awsRegion ?? "")
+    const [resolved] = mergeSecrets(
+        [parsed.data],
+        sameEndpoint && stored ? [stored] : [],
+    )
+
+    return validateModel(
+        new Request(new URL("/api/validate-model", req.url), {
+            method: "POST",
+            headers: { "Content-Type": "application/json" },
+            body: JSON.stringify({
+                provider: resolved.provider,
+                apiKey: resolved.apiKey,
+                baseUrl: resolved.baseUrl,
+                modelId: body.modelId,
+                awsAccessKeyId: resolved.awsAccessKeyId,
+                awsSecretAccessKey: resolved.awsSecretAccessKey,
+                awsRegion: resolved.awsRegion,
+                vertexApiKey: resolved.vertexApiKey,
+            }),
+        }),
+    )
+}

app/api/validate-model/route.ts

@@ -51,7 +51,7 @@ export async function POST(req: Request) {
         }
 
         // SECURITY: Block SSRF attacks via custom baseUrl
-        if (baseUrl && !allowPrivateUrls && isPrivateUrl(baseUrl)) {
+        if (baseUrl && !allowPrivateUrls() && isPrivateUrl(baseUrl)) {
             return NextResponse.json(
                 { valid: false, error: "Invalid base URL" },
                 { status: 400 },