feat: Implement centralized audit logging admin interface (refs #10)

- Add audit_logs table with categories, severities, and indexes
- Create AuditLogService and AuditLogRepository
- Add REST API endpoints for viewing and exporting logs
- Wire audit logging into auth, vehicles, admin, and backup features
- Add desktop AdminLogsPage with filters and CSV export
- Add mobile AdminLogsMobileScreen with card layout
- Implement 90-day retention cleanup job
- Remove old AuditLogPanel from AdminCatalogPage

Security fixes:
- Escape LIKE special characters to prevent pattern injection
- Limit CSV export to 5000 records to prevent memory exhaustion
- Add truncation warning headers for large exports

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/features/admin/api/admin.api.ts

@@ -49,6 +49,9 @@ import {
   UpdateScheduleRequest,
   RestorePreviewResponse,
   ExecuteRestoreRequest,
+  // Unified Audit Log types
+  UnifiedAuditLogsResponse,
+  AuditLogFilters,
 } from '../types/admin.types';
 
 export interface AuditLogsResponse {
@@ -507,4 +510,36 @@ export const adminApi = {
       },
     },
   },
+
+  // Unified Audit Logs (new centralized audit system)
+  unifiedAuditLogs: {
+    list: async (filters: AuditLogFilters = {}): Promise<UnifiedAuditLogsResponse> => {
+      const params: Record<string, string | number> = {};
+      if (filters.search) params.search = filters.search;
+      if (filters.category) params.category = filters.category;
+      if (filters.severity) params.severity = filters.severity;
+      if (filters.startDate) params.startDate = filters.startDate;
+      if (filters.endDate) params.endDate = filters.endDate;
+      if (filters.limit) params.limit = filters.limit;
+      if (filters.offset) params.offset = filters.offset;
+
+      const response = await apiClient.get<UnifiedAuditLogsResponse>('/admin/audit-logs', { params });
+      return response.data;
+    },
+
+    export: async (filters: AuditLogFilters = {}): Promise<Blob> => {
+      const params: Record<string, string | number> = {};
+      if (filters.search) params.search = filters.search;
+      if (filters.category) params.category = filters.category;
+      if (filters.severity) params.severity = filters.severity;
+      if (filters.startDate) params.startDate = filters.startDate;
+      if (filters.endDate) params.endDate = filters.endDate;
+
+      const response = await apiClient.get('/admin/audit-logs/export', {
+        params,
+        responseType: 'blob',
+      });
+      return response.data;
+    },
+  },
 };