feat(admin): visual theme cards, album search, and status dashboard (#241)

* feat(admin): implement visual theme cards, album search, and system status diagnostics

* fix(admin): resolve type-checking build errors in SettingsEditor and status route

---------

Co-authored-by: ralksta <ralksta@users.noreply.github.com>

app/api/admin/status/route.ts

@@ -0,0 +1,75 @@
+import { NextResponse } from 'next/server';
+import { isAdminAuthenticated, isAdminEnabled } from '@/lib/admin/auth';
+import { immich } from '@/lib/immich';
+import { cache } from '@/lib/cache';
+import { listBackups, readGalleryYaml, readSettingsYaml } from '@/lib/admin/yaml-service';
+
+export async function GET() {
+  if (!isAdminEnabled()) {
+    return NextResponse.json({ error: 'Admin not enabled' }, { status: 403 });
+  }
+  if (!(await isAdminAuthenticated())) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  // 1. Immich Connection Status
+  let immichOk = false;
+  try {
+    immichOk = await immich.ping();
+  } catch (err) {
+    console.error('[Admin API] Immich ping failed:', err);
+  }
+
+  // 2. Config Health Check
+  let galleryValid = false;
+  let settingsValid = false;
+  try {
+    const gallery = await readGalleryYaml();
+    galleryValid = !!gallery;
+  } catch (err) {
+    console.error('[Admin API] Gallery YAML parse failed:', err);
+  }
+
+  try {
+    const settings = await readSettingsYaml();
+    settingsValid = !!settings;
+  } catch (err) {
+    console.error('[Admin API] Settings YAML parse failed:', err);
+  }
+
+  // 3. Backup Info
+  const galleryBackups = await listBackups('gallery.yaml');
+  const settingsBackups = await listBackups('settings.yaml');
+  const backupCount = galleryBackups.length + settingsBackups.length;
+  
+  // Find timestamp of the latest backup
+  let lastBackup: string | null = null;
+  const allBackups = [...galleryBackups, ...settingsBackups].sort().reverse();
+  if (allBackups.length > 0) {
+    // Filename format: filename.yaml.2026-05-31T17-30-00-000Z.bak
+    const match = allBackups[0].match(/\d{4}-\d{2}-\d{2}T\d{2}-\d{2}-\d{2}/);
+    if (match) {
+      lastBackup = match[0].replace(/-/g, ':').replace(/(\d{4}):(\d{2}):(\d{2})T/, '$1-$2-$3T');
+    } else {
+      lastBackup = allBackups[0]; // fallback
+    }
+  }
+
+  return NextResponse.json({
+    immich: {
+      status: immichOk ? 'connected' : 'disconnected',
+    },
+    config: {
+      status: (galleryValid && settingsValid) ? 'valid' : 'invalid',
+      gallery: galleryValid ? 'valid' : 'invalid',
+      settings: settingsValid ? 'valid' : 'invalid',
+    },
+    cache: {
+      size: cache.size,
+    },
+    backups: {
+      count: backupCount,
+      lastBackup,
+    },
+  });
+}