refactor(backend): standardize error responses, logging, pagination

- errorResponse(res, error, status, publicMessage) in routeHelpers,
  wired into 125 catch blocks across 10 route files; wire format
  ({ error: <string> }) unchanged byte-for-byte
- Replace remaining console.* with logger across src (178 sites);
  3 intentional console sites kept (install boot, unbound .catch ref)
- Adopt getPagination in 6 routes where semantics match exactly

backend/src/middleware/maintenance.js

@@ -1,4 +1,5 @@
 const { db } = require('../database/db');
+const logger = require('../utils/logger');
 
 // Cache maintenance mode status to avoid DB queries on every request
 let maintenanceMode = false;
@@ -26,7 +27,7 @@ async function queryWithRetry(queryFn, retries = MAX_RETRIES) {
         error.code === 'ECONNRESET';
       
       if (isConnectionError) {
-        console.warn(`Database connection error, retrying in ${RETRY_DELAY}ms... (attempt ${i + 1}/${retries})`);
+        logger.warn(`Database connection error, retrying in ${RETRY_DELAY}ms... (attempt ${i + 1}/${retries})`);
         await new Promise(resolve => setTimeout(resolve, RETRY_DELAY));
       } else {
         throw error; // Don't retry non-connection errors
@@ -56,7 +57,7 @@ async function checkMaintenanceMode() {
     
     return maintenanceMode;
   } catch (error) {
-    console.error('Error checking maintenance mode after retries:', error.message);
+    logger.error('Error checking maintenance mode after retries:', error.message);
     // Return cached value or false if no cache
     return maintenanceMode;
   }
@@ -102,7 +103,7 @@ async function maintenanceMiddleware(req, res, next) {
     }
   } catch (error) {
     // If we can't check maintenance mode, allow the request to proceed
-    console.error('Failed to check maintenance mode, allowing request:', error.message);
+    logger.error('Failed to check maintenance mode, allowing request:', error.message);
   }
   
   next();

backend/src/middleware/secureImageMiddleware.js

@@ -333,7 +333,7 @@ class SecureImageMiddleware {
         await db('security_logs').insert(logData).catch(console.error);
       }
     } catch (error) {
-      console.error('Error logging security event:', error);
+      logger.error('Error logging security event:', error);
     }
   }
 
@@ -363,7 +363,7 @@ class SecureImageMiddleware {
         perHour: config.perHour || 500
       };
     } catch (error) {
-      console.error('Error getting rate limit settings:', error);
+      logger.error('Error getting rate limit settings:', error);
       return { perMinute: 30, per5Minutes: 100, perHour: 500 };
     }
   }

backend/src/middleware/secureStatic.js

@@ -1,6 +1,7 @@
 const path = require('path');
 const express = require('express');
 const { safePathJoin, isPathSafe } = require('../utils/fileSecurityUtils');
+const logger = require('../utils/logger');
 
 /**
  * Create a secure static file serving middleware that prevents path traversal attacks
@@ -17,7 +18,7 @@ function secureStatic(basePath, options = {}) {
     
     // Validate the path doesn't contain dangerous patterns
     if (!isPathSafe(requestedPath)) {
-      console.warn(`Potential path traversal attempt blocked: ${requestedPath}`);
+      logger.warn(`Potential path traversal attempt blocked: ${requestedPath}`);
       return res.status(403).json({ error: 'Access denied' });
     }
     
@@ -52,7 +53,7 @@ function secureStatic(basePath, options = {}) {
       return staticMiddleware(req, res, next);
     } catch (error) {
       // Path traversal detected
-      console.error(`Path traversal blocked: ${requestedPath}`, error.message);
+      logger.error(`Path traversal blocked: ${requestedPath}`, error.message);
       return res.status(403).json({ error: 'Access denied' });
     }
   };

backend/src/middleware/sessionTimeout.js

@@ -1,6 +1,7 @@
 const jwt = require('jsonwebtoken');
 const { db } = require('../database/db');
 const { getAdminTokenFromRequest } = require('../utils/tokenUtils');
+const logger = require('../utils/logger');
 
 // In-memory session tracking (in production, use Redis)
 const sessions = new Map();
@@ -69,7 +70,7 @@ async function getSessionTimeout() {
   } catch (error) {
     // Only log if it's not a connection error (to avoid spam)
     if (error.code !== 'ECONNRESET' && !error.message?.includes('Connection terminated')) {
-      console.error('Error getting session timeout:', error.message);
+      logger.error('Error getting session timeout:', error.message);
     }
   }