Add database maintenance tooling

- Implement maintenance hooks (useMaintenanceTables, useVacuumTable, useAnalyzeTable, useReindexTable)
- Add DatabaseMaintenance page and UI for vacuum/analyze/reindex
- Wire new route / admin/database-maintenance and sidebar entry
- Remove DatabaseMaintenance icon usage on page and align with AdminLayout props

src/lib/queryKeys.ts

@@ -103,6 +103,7 @@ export const queryKeys = {
   admin: {
     databaseStats: () => ['admin', 'database-stats'] as const,
     recentAdditions: (limit: number) => ['admin', 'recent-additions', limit] as const,
+    maintenanceTables: () => ['admin', 'maintenance-tables'] as const,
   },
   
   // Analytics queries