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/auth/api/auth.controller.ts

@@ -11,6 +11,7 @@ import { termsConfig } from '../../terms-agreement/domain/terms-config';
 import { pool } from '../../../core/config/database';
 import { logger } from '../../../core/logging/logger';
 import { signupSchema, resendVerificationPublicSchema } from './auth.validation';
+import { auditLogService } from '../../audit-log';
 
 export class AuthController {
   private authService: AuthService;
@@ -66,6 +67,16 @@ export class AuthController {
 
       logger.info('User signup successful', { email, userId: result.userId });
 
+      // Log signup to unified audit log
+      await auditLogService.info(
+        'auth',
+        result.userId,
+        `User signup: ${email}`,
+        'user',
+        result.userId,
+        { email, ipAddress: termsData.ipAddress }
+      ).catch(err => logger.error('Failed to log signup audit event', { error: err }));
+
       return reply.code(201).send(result);
     } catch (error: any) {
       logger.error('Signup failed', { error, email: (request.body as any)?.email });
@@ -254,6 +265,15 @@ export class AuthController {
         userId: userId.substring(0, 8) + '...',
       });
 
+      // Log password reset request to unified audit log
+      await auditLogService.info(
+        'auth',
+        userId,
+        'Password reset requested',
+        'user',
+        userId
+      ).catch(err => logger.error('Failed to log password reset audit event', { error: err }));
+
       return reply.code(200).send(result);
     } catch (error: any) {
       logger.error('Failed to request password reset', {