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.

docs/cn/README_CN.md

@@ -222,6 +222,12 @@ npm run dev
 
 注意：`claude` 系列已在带有 AWS、Azure、GCP 等云架构 Logo 的 draw.io 图表上进行训练，因此如果您想创建云架构图，这是最佳选择。
 
+### 管理面板
+
+设置 `ADMIN_PASSWORD` 环境变量并访问 `/admin`，即可在 Web 面板中管理服务端设置（模型、访问码、功能开关、可观测性、配额），无需手动编辑 `.env`。
+
+📖 **[管理面板指南](./admin-panel.md)** — 启用方法、优先级规则和注意事项。
+
 
 ## 工作原理
 

docs/cn/admin-panel.md

@@ -0,0 +1,24 @@
+# 管理面板
+
+无需手动编辑 `.env`，您可以在 Web 管理面板中管理服务端设置。
+
+## 启用面板
+
+1. 设置 `ADMIN_PASSWORD` 环境变量（不设置则面板禁用）。
+2. 访问 `/admin` 并登录。
+
+## 可配置内容
+
+1. **Models（模型）** — 添加提供商及其 API Key 和模型列表，交互与应用内的模型设置相同。保存后这些模型成为所有用户可用的服务端模型，并在请求时与环境中的 `AI_MODELS_CONFIG` / `ai-models.json` 合并（面板不会修改这些环境文件）。
+2. **其余区块** — 访问码、生成参数、功能开关、可观测性和配额。保存的设置会写入 `data/settings.json` 并立即生效，无需重启（少数设置如 Langfuse 和 DynamoDB 标记为"需要重启"）。
+
+## 优先级
+
+面板中保存的设置覆盖环境变量，环境变量覆盖内置默认值。删除已保存的值会回退到环境变量。
+
+## 注意事项
+
+- 密钥以明文形式存储在 `data/settings.json` 中（文件权限 600），请妥善保管该文件。
+- 在无服务器平台（Vercel、Cloudflare Workers）上没有持久化磁盘，面板为只读 — 请改用环境变量配置。
+- 使用 Docker 时，`data/` 目录通过 `docker-compose.yml` 中的卷持久化。
+- `NEXT_PUBLIC_*` 变量在构建时固化，无法在面板中修改。

docs/en/admin-panel.md

@@ -0,0 +1,24 @@
+# Admin Panel
+
+Instead of hand-editing `.env`, you can manage server settings in a web admin panel.
+
+## Enabling the panel
+
+1. Set the `ADMIN_PASSWORD` environment variable (leave unset to disable the panel).
+2. Visit `/admin` and sign in.
+
+## What you can configure
+
+1. **Models** — add providers with their API keys and model lists, using the same UI as the in-app model settings. Saved models become server-side models available to all users, merged with any `AI_MODELS_CONFIG` / `ai-models.json` from your environment at request time (the panel does not modify those env files).
+2. **Other sections** — access codes, generation parameters, features, observability, and quota. Saved settings are written to `data/settings.json` and apply immediately — no restart needed (a few settings such as Langfuse and DynamoDB are marked "Restart Required").
+
+## Precedence
+
+Settings saved in the panel override environment variables, which override built-in defaults. Removing a saved value falls back to the environment variable.
+
+## Notes
+
+- Secrets are stored in plaintext in `data/settings.json` (file mode 600). Keep the file private.
+- On serverless platforms (Vercel, Cloudflare Workers) there is no persistent disk, so the panel is read-only — configure via environment variables there.
+- With Docker, the `data/` directory is persisted via the volume in `docker-compose.yml`.
+- `NEXT_PUBLIC_*` variables are baked in at build time and cannot be changed in the panel.

docs/ja/README_JA.md

@@ -221,6 +221,12 @@ AWS BedrockとOpenRouter以外のすべてのプロバイダーはカスタム
 
 注：`claude`シリーズはAWS、Azure、GCPなどのクラウドアーキテクチャロゴ付きのdraw.ioダイアグラムで学習されているため、クラウドアーキテクチャダイアグラムを作成したい場合は最適な選択です。
 
+### 管理パネル
+
+`ADMIN_PASSWORD` 環境変数を設定して `/admin` にアクセスすると、`.env` を手動で編集する代わりに Web パネルでサーバー設定（モデル、アクセスコード、機能、可観測性、クォータ）を管理できます。
+
+📖 **[管理パネルガイド](./admin-panel.md)** — 有効化の方法、優先順位ルール、注意事項。
+
 
 ## 仕組み
 

docs/ja/admin-panel.md

@@ -0,0 +1,24 @@
+# 管理パネル
+
+`.env` を手動で編集する代わりに、Web 管理パネルでサーバー設定を管理できます。
+
+## パネルの有効化
+
+1. `ADMIN_PASSWORD` 環境変数を設定します（未設定の場合、パネルは無効になります）。
+2. `/admin` にアクセスしてサインインします。
+
+## 設定できる項目
+
+1. **Models（モデル）** — アプリ内のモデル設定と同じ UI で、プロバイダーの API キーとモデルリストを追加します。保存するとそれらは全ユーザーが利用できるサーバーサイドモデルになり、リクエスト時に環境の `AI_MODELS_CONFIG` / `ai-models.json` とマージされます（パネルがこれらの環境ファイルを変更することはありません）。
+2. **その他のセクション** — アクセスコード、生成パラメータ、機能、可観測性、クォータ。保存された設定は `data/settings.json` に書き込まれ、即座に反映されます — 再起動は不要です（Langfuse や DynamoDB など一部の設定は「再起動が必要」と表示されます）。
+
+## 優先順位
+
+パネルで保存された設定は環境変数を上書きし、環境変数は組み込みのデフォルト値を上書きします。保存した値を削除すると環境変数にフォールバックします。
+
+## 注意事項
+
+- シークレットは `data/settings.json` に平文で保存されます（ファイルモード 600）。このファイルは非公開に保ってください。
+- サーバーレスプラットフォーム（Vercel、Cloudflare Workers）には永続ディスクがないため、パネルは読み取り専用です — その環境では環境変数で設定してください。
+- Docker 使用時は、`data/` ディレクトリが `docker-compose.yml` のボリュームで永続化されます。
+- `NEXT_PUBLIC_*` 変数はビルド時に固定され、パネルでは変更できません。