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.

lib/server-model-config.ts

@@ -62,7 +62,7 @@ function getConfigPath(): string {
     return path.join(process.cwd(), "ai-models.json")
 }
 
-export async function loadRawServerModelsConfig(): Promise<ServerModelsConfig | null> {
+export async function loadEnvServerModelsConfig(): Promise<ServerModelsConfig | null> {
     // Priority 1: AI_MODELS_CONFIG env var (JSON string) - for cloud deployments
     const envConfig = process.env.AI_MODELS_CONFIG
     if (envConfig && envConfig.trim().length > 0) {
@@ -96,6 +96,40 @@ export async function loadRawServerModelsConfig(): Promise<ServerModelsConfig |
     }
 }
 
+export async function loadRawServerModelsConfig(): Promise<ServerModelsConfig | null> {
+    const envConfig = await loadEnvServerModelsConfig()
+
+    // Merge in providers managed via the admin panel (settings.json).
+    // Dynamic import to avoid a module-init cycle with lib/admin/providers.
+    let adminConfig: ServerModelsConfig | null = null
+    try {
+        const { adminProvidersToConfig, loadAdminProviders } = await import(
+            "./admin/providers"
+        )
+        const adminProviders = loadAdminProviders()
+        if (adminProviders.length > 0) {
+            adminConfig = adminProvidersToConfig(adminProviders)
+        }
+    } catch (err) {
+        console.error(
+            "[server-model-config] Failed to load admin providers:",
+            err,
+        )
+    }
+
+    if (!adminConfig || adminConfig.providers.length === 0) return envConfig
+    if (!envConfig) return adminConfig
+
+    // A panel default overrides an env default
+    const adminHasDefault = adminConfig.providers.some((p) => p.default)
+    const envProviders = adminHasDefault
+        ? envConfig.providers.map((p) =>
+              p.default ? { ...p, default: undefined } : p,
+          )
+        : envConfig.providers
+    return { providers: [...envProviders, ...adminConfig.providers] }
+}
+
 export async function loadFlattenedServerModels(): Promise<
     FlattenedServerModel[]
 > {