feat(admin): add cache purge controls to settings

Add `purgeMetadataCache` and `purgeImageCache` procedures that let admins free disk space on demand. Metadata purge removes un-enriched stub titles not in any user's library plus orphaned person records; image purge deletes all cached TMDB files from disk.

Expose both as POST endpoints under `/admin/cache/` via the oRPC contract, implement the core logic in a new `@sofa/core/cache` module, and surface them in a new "Danger Zone" section on the Settings page with individual confirmation dialogs and a combined "Purge all" action.

apps/server/src/orpc/procedures/admin.ts

@@ -8,6 +8,10 @@ import {
   listBackups,
   restoreFromBackup,
 } from "@sofa/core/backup";
+import {
+  purgeImageCache as purgeImagesFn,
+  purgeMetadataCache as purgeMetadataFn,
+} from "@sofa/core/cache";
 import { getSetting, setSetting } from "@sofa/core/settings";
 import { isTelemetryEnabled } from "@sofa/core/telemetry";
 import {
@@ -159,3 +163,13 @@ export const triggerJob = os.admin.triggerJob
     }
     return { ok: true as const };
   });
+
+// ─── Purge ────────────────────────────────────────────────────
+
+export const purgeMetadataCache = os.admin.purgeMetadataCache
+  .use(admin)
+  .handler(() => purgeMetadataFn());
+
+export const purgeImageCache = os.admin.purgeImageCache
+  .use(admin)
+  .handler(async () => purgeImagesFn());

apps/server/src/orpc/router.ts

@@ -81,6 +81,8 @@ export const implementedRouter = {
     telemetry: admin.telemetry,
     toggleTelemetry: admin.toggleTelemetry,
     triggerJob: admin.triggerJob,
+    purgeMetadataCache: admin.purgeMetadataCache,
+    purgeImageCache: admin.purgeImageCache,
   },
   account: {
     updateName: account.updateName,