feat(admin): wire instance health panel + settings instance (A9/A10)

AdminInstance shows backing-service health (db/redis/ml), read-only source
status (env-configured), and a library reindex with graceful handling when no
indexable source exists. InstanceSettings shows the active instance and offers
switch/sign-out to /connect. Adds getServices/getSources/reindex endpoints.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/api/endpoints/admin.ts

@@ -1,6 +1,11 @@
 import { api } from '../index';
 import { toUser, type RawUser } from '../mappers';
-import type { User } from '../types';
+import type { User, ServicesStatus, SourceInfo } from '../types';
+
+interface ReindexJob {
+  source: string;
+  jobId: string;
+}
 
 /**
  * Admin user management. The backend models authorization as `is_superuser` /
@@ -59,6 +64,20 @@ export const adminApi = api.injectEndpoints({
         body: { new_password: newPassword },
       }),
     }),
+    // -- instance (§A9) -------------------------------------------------------
+    getServices: build.query<ServicesStatus, void>({
+      query: () => '/admin/services',
+    }),
+    getSources: build.query<SourceInfo[], void>({
+      query: () => '/admin/sources',
+    }),
+    reindex: build.mutation<ReindexJob[], void>({
+      query: () => ({ url: '/admin/reindex', method: 'POST' }),
+      transformResponse: (raw: { jobs: { source: string; job_id: string }[] }) =>
+        raw.jobs.map((j) => ({ source: j.source, jobId: j.job_id })),
+      // A fresh scan changes the catalogue once the worker runs.
+      invalidatesTags: ['Track', 'Album', 'Artist', 'Storage'],
+    }),
   }),
   overrideExisting: false,
 });
@@ -70,4 +89,7 @@ export const {
   useUpdateUserMutation,
   useDeleteUserMutation,
   useResetPasswordMutation,
+  useGetServicesQuery,
+  useGetSourcesQuery,
+  useReindexMutation,
 } = adminApi;