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/admin/domain/admin.service.ts

@@ -6,6 +6,7 @@
 import { AdminRepository } from '../data/admin.repository';
 import { AdminUser, AdminAuditLog } from './admin.types';
 import { logger } from '../../../core/logging/logger';
+import { auditLogService } from '../../audit-log';
 
 export class AdminService {
   constructor(private repository: AdminRepository) {}
@@ -58,12 +59,22 @@ export class AdminService {
       // Create new admin
       const admin = await this.repository.createAdmin(auth0Sub, normalizedEmail, role, createdBy);
 
-      // Log audit action
+      // Log audit action (legacy)
       await this.repository.logAuditAction(createdBy, 'CREATE', admin.auth0Sub, 'admin_user', admin.email, {
         email,
         role
       });
 
+      // Log to unified audit log
+      await auditLogService.info(
+        'admin',
+        createdBy,
+        `Admin user created: ${admin.email}`,
+        'admin_user',
+        admin.auth0Sub,
+        { email: admin.email, role }
+      ).catch(err => logger.error('Failed to log admin create audit event', { error: err }));
+
       logger.info('Admin user created', { email, role });
       return admin;
     } catch (error) {
@@ -83,9 +94,19 @@ export class AdminService {
       // Revoke the admin
       const admin = await this.repository.revokeAdmin(auth0Sub);
 
-      // Log audit action
+      // Log audit action (legacy)
       await this.repository.logAuditAction(revokedBy, 'REVOKE', auth0Sub, 'admin_user', admin.email);
 
+      // Log to unified audit log
+      await auditLogService.info(
+        'admin',
+        revokedBy,
+        `Admin user revoked: ${admin.email}`,
+        'admin_user',
+        auth0Sub,
+        { email: admin.email }
+      ).catch(err => logger.error('Failed to log admin revoke audit event', { error: err }));
+
       logger.info('Admin user revoked', { auth0Sub, email: admin.email });
       return admin;
     } catch (error) {
@@ -99,9 +120,19 @@ export class AdminService {
       // Reinstate the admin
       const admin = await this.repository.reinstateAdmin(auth0Sub);
 
-      // Log audit action
+      // Log audit action (legacy)
       await this.repository.logAuditAction(reinstatedBy, 'REINSTATE', auth0Sub, 'admin_user', admin.email);
 
+      // Log to unified audit log
+      await auditLogService.info(
+        'admin',
+        reinstatedBy,
+        `Admin user reinstated: ${admin.email}`,
+        'admin_user',
+        auth0Sub,
+        { email: admin.email }
+      ).catch(err => logger.error('Failed to log admin reinstate audit event', { error: err }));
+
       logger.info('Admin user reinstated', { auth0Sub, email: admin.email });
       return admin;
     } catch (error) {