feat: implement dynamic rate limiting with database configuration

- Add database migration for rate limit settings
- Create rate limit service with dynamic configuration from database
- Implement proper authentication detection for admin and gallery tokens
- Skip rate limiting for authenticated users (configurable)
- Add admin API endpoint to update rate limit settings
- Use correct client IP detection with proxy support
- Cache settings for performance (1 minute cache)
- Default to 1000 requests per 15 minutes for better UX
- Apply auth-specific limits only to login endpoints

Key improvements:
- No more rate limiting for authenticated gallery/admin users
- Configurable via admin settings page
- Immediate effect when settings change
- Better handling of proxied requests

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

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

backend/src/routes/adminSettings.js

@@ -7,6 +7,7 @@ const { db, logActivity } = require('../database/db');
 const { formatBoolean } = require('../utils/dbCompat');
 const { adminAuth } = require('../middleware/auth');
 const { clearMaintenanceCache } = require('../middleware/maintenance');
+const { clearSettingsCache } = require('../services/rateLimitService');
 const router = express.Router();
 
 // Configure multer for logo uploads
@@ -582,4 +583,68 @@ router.post('/favicon', adminAuth, faviconUpload.single('favicon'), async (req,
   }
 });
 
+// Update rate limit settings
+router.put('/security/rate-limit', adminAuth, [
+  body('rate_limit_enabled').isBoolean().withMessage('Enabled must be a boolean'),
+  body('rate_limit_window_minutes').isInt({ min: 1, max: 60 }).withMessage('Window must be between 1 and 60 minutes'),
+  body('rate_limit_max_requests').isInt({ min: 10, max: 10000 }).withMessage('Max requests must be between 10 and 10000'),
+  body('rate_limit_auth_max_requests').isInt({ min: 1, max: 100 }).withMessage('Auth max requests must be between 1 and 100'),
+  body('rate_limit_skip_authenticated').isBoolean().withMessage('Skip authenticated must be a boolean'),
+  body('rate_limit_public_endpoints_only').isBoolean().withMessage('Public endpoints only must be a boolean')
+], async (req, res) => {
+  try {
+    const errors = validationResult(req);
+    if (!errors.isEmpty()) {
+      return res.status(400).json({ errors: errors.array() });
+    }
+
+    const {
+      rate_limit_enabled,
+      rate_limit_window_minutes,
+      rate_limit_max_requests,
+      rate_limit_auth_max_requests,
+      rate_limit_skip_authenticated,
+      rate_limit_public_endpoints_only
+    } = req.body;
+
+    // Update each setting
+    const settings = [
+      { key: 'rate_limit_enabled', value: rate_limit_enabled },
+      { key: 'rate_limit_window_minutes', value: rate_limit_window_minutes },
+      { key: 'rate_limit_max_requests', value: rate_limit_max_requests },
+      { key: 'rate_limit_auth_max_requests', value: rate_limit_auth_max_requests },
+      { key: 'rate_limit_skip_authenticated', value: rate_limit_skip_authenticated },
+      { key: 'rate_limit_public_endpoints_only', value: rate_limit_public_endpoints_only }
+    ];
+
+    for (const { key, value } of settings) {
+      await db('app_settings')
+        .where('setting_key', key)
+        .update({
+          setting_value: JSON.stringify(value),
+          updated_at: new Date()
+        });
+    }
+
+    // Clear the rate limit settings cache to apply changes immediately
+    clearSettingsCache();
+
+    // Log activity
+    await logActivity('settings_updated', 
+      { 
+        category: 'security',
+        subcategory: 'rate_limit',
+        changes: settings.length
+      },
+      null,
+      { type: 'admin', id: req.admin.id, name: req.admin.username }
+    );
+
+    res.json({ message: 'Rate limit settings updated successfully' });
+  } catch (error) {
+    console.error('Rate limit settings update error:', error);
+    res.status(500).json({ error: 'Failed to update rate limit settings' });
+  }
+});
+
 module.exports = router;