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>

backend/src/features/audit-log/README.md

@@ -0,0 +1,168 @@
+# Audit Log Feature
+
+Centralized audit logging system for tracking all user and system actions across MotoVaultPro.
+
+## Architecture
+
+```
+                        Frontend
+  +--------------+  +-------------------+
+  | AdminLogsPage|  | AdminLogsMobile   |
+  | (desktop)    |  | Screen (mobile)   |
+  +------+-------+  +--------+----------+
+         |                   |
+         +-------------------+
+                 |
+                 | useAuditLogs hook
+                 v
+           adminApi.unifiedAuditLogs
+                 |
+                 | HTTP
+                 v
+  GET /api/admin/audit-logs?search=X&category=Y&...
+  GET /api/admin/audit-logs/export
+                 |
+        +--------v--------+
+        | AuditLogController |
+        +--------+--------+
+                 |
+        +--------v--------+
+        |  AuditLogService  |<----- Other services call
+        |  log(category,...)|       auditLogService.info()
+        +--------+--------+
+                 |
+        +--------v--------+
+        | AuditLogRepository |
+        +--------+--------+
+                 v
+          +-------------+
+          |  audit_logs | (PostgreSQL)
+          +-------------+
+```
+
+## Data Flow
+
+```
+Feature Service (vehicles, auth, etc.)
+        |
+        | auditLogService.info(category, userId, action, resourceType?, resourceId?, details?)
+        v
+  AuditLogService
+        |
+        | INSERT INTO audit_logs
+        v
+  PostgreSQL audit_logs table
+        |
+        | GET /api/admin/audit-logs (with filters)
+        v
+  AdminLogsPage/Mobile displays filtered, paginated results
+```
+
+## Database Schema
+
+```sql
+CREATE TABLE audit_logs (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  category VARCHAR(20) NOT NULL CHECK (category IN ('auth', 'vehicle', 'user', 'system', 'admin')),
+  severity VARCHAR(10) NOT NULL CHECK (severity IN ('info', 'warning', 'error')),
+  user_id VARCHAR(255),        -- NULL for system-initiated actions
+  action VARCHAR(500) NOT NULL,
+  resource_type VARCHAR(100),
+  resource_id VARCHAR(255),
+  details JSONB,
+  created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+```
+
+## Indexes
+
+- `idx_audit_logs_category_created` - B-tree for category filtering
+- `idx_audit_logs_severity_created` - B-tree for severity filtering
+- `idx_audit_logs_user_created` - B-tree for user filtering
+- `idx_audit_logs_created` - B-tree for date ordering
+- `idx_audit_logs_action_gin` - GIN trigram for text search
+
+## API Endpoints
+
+### GET /api/admin/audit-logs
+
+Returns paginated audit logs with optional filters.
+
+**Query Parameters:**
+- `search` - Text search on action field (ILIKE)
+- `category` - Filter by category (auth, vehicle, user, system, admin)
+- `severity` - Filter by severity (info, warning, error)
+- `startDate` - ISO date string for date range start
+- `endDate` - ISO date string for date range end
+- `limit` - Page size (default 25, max 100)
+- `offset` - Pagination offset
+
+**Response:**
+```json
+{
+  "logs": [
+    {
+      "id": "uuid",
+      "category": "vehicle",
+      "severity": "info",
+      "userId": "auth0|...",
+      "action": "Vehicle created: 2024 Toyota Camry",
+      "resourceType": "vehicle",
+      "resourceId": "vehicle-uuid",
+      "details": { "vin": "...", "make": "Toyota" },
+      "createdAt": "2024-01-15T10:30:00Z"
+    }
+  ],
+  "total": 150,
+  "limit": 25,
+  "offset": 0
+}
+```
+
+### GET /api/admin/audit-logs/export
+
+Returns CSV file with filtered audit logs.
+
+**Query Parameters:** Same as list endpoint (except pagination)
+
+**Response:** CSV file download
+
+## Usage in Features
+
+```typescript
+import { auditLogService } from '../../audit-log';
+
+// In vehicles.service.ts
+await auditLogService.info(
+  'vehicle',
+  userId,
+  `Vehicle created: ${vehicleDesc}`,
+  'vehicle',
+  vehicleId,
+  { vin, make, model, year }
+).catch(err => logger.error('Failed to log audit event', { error: err }));
+```
+
+## Retention Policy
+
+- Logs older than 90 days are automatically deleted
+- Cleanup job runs daily at 3 AM
+- Implemented in `jobs/cleanup.job.ts`
+
+## Categories
+
+| Category | Description | Examples |
+|----------|-------------|----------|
+| `auth` | Authentication events | Signup, password reset |
+| `vehicle` | Vehicle CRUD | Create, update, delete |
+| `user` | User management | Profile updates |
+| `system` | System operations | Backup, restore |
+| `admin` | Admin actions | Grant/revoke admin |
+
+## Severity Levels
+
+| Level | Color (UI) | Description |
+|-------|------------|-------------|
+| `info` | Blue | Normal operations |
+| `warning` | Yellow | Potential issues |
+| `error` | Red | Failed operations |