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/jobs/cleanup.job.ts

@@ -0,0 +1,74 @@
+/**
+ * @ai-summary Job for audit log retention cleanup
+ * @ai-context Runs daily at 3 AM to delete logs older than 90 days
+ */
+
+import { Pool } from 'pg';
+import { logger } from '../../../core/logging/logger';
+import { AuditLogService } from '../domain/audit-log.service';
+import { AuditLogRepository } from '../data/audit-log.repository';
+
+let pool: Pool | null = null;
+
+/**
+ * Sets the database pool for the job
+ */
+export function setAuditLogCleanupJobPool(dbPool: Pool): void {
+  pool = dbPool;
+}
+
+/**
+ * Retention period in days for audit logs
+ */
+const AUDIT_LOG_RETENTION_DAYS = 90;
+
+/**
+ * Result of cleanup job
+ */
+export interface AuditLogCleanupResult {
+  deletedCount: number;
+  retentionDays: number;
+  success: boolean;
+  error?: string;
+}
+
+/**
+ * Processes audit log retention cleanup
+ */
+export async function processAuditLogCleanup(): Promise<AuditLogCleanupResult> {
+  if (!pool) {
+    throw new Error('Database pool not initialized for audit log cleanup job');
+  }
+
+  const repository = new AuditLogRepository(pool);
+  const service = new AuditLogService(repository);
+
+  try {
+    logger.info('Starting audit log cleanup job', {
+      retentionDays: AUDIT_LOG_RETENTION_DAYS,
+    });
+
+    const deletedCount = await service.cleanup(AUDIT_LOG_RETENTION_DAYS);
+
+    logger.info('Audit log cleanup job completed', {
+      deletedCount,
+      retentionDays: AUDIT_LOG_RETENTION_DAYS,
+    });
+
+    return {
+      deletedCount,
+      retentionDays: AUDIT_LOG_RETENTION_DAYS,
+      success: true,
+    };
+  } catch (error) {
+    const errorMessage = error instanceof Error ? error.message : String(error);
+    logger.error('Audit log cleanup job failed', { error: errorMessage });
+
+    return {
+      deletedCount: 0,
+      retentionDays: AUDIT_LOG_RETENTION_DAYS,
+      success: false,
+      error: errorMessage,
+    };
+  }
+}