fix: production deployment issues with Traefik and database migrations

- Add missing created_at column to email_queue table
- Fix 502 Bad Gateway errors with proper Traefik routing configuration
- Create docker-compose.traefik.yml for external Traefik deployment
- Fix health check endpoint path for API path stripping
- Add PostgreSQL init script for Umami database creation
- Add comprehensive deployment guide for Traefik setup

The backend now properly handles /api prefix stripping by Traefik and
migrations run safely in production environments with existing schemas.

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

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

backend/server.js

@@ -10,7 +10,7 @@ const cors = require('cors');
 const rateLimit = require('express-rate-limit');
 const jwt = require('jsonwebtoken');
 const path = require('path');
-const { initializeDatabase } = require('./src/database/db');
+const { initializeDatabase, db } = require('./src/database/db');
 const { startFileWatcher } = require('./src/services/fileWatcher');
 const { startExpirationChecker } = require('./src/services/expirationChecker');
 const { initializeTransporter, startEmailQueueProcessor } = require('./src/services/emailProcessor');
@@ -152,7 +152,7 @@ app.use('/thumbnails', require('./src/middleware/photoAuth'), setCorsHeaders, se
 app.use('/uploads', setCorsHeaders, secureStatic(path.join(__dirname, 'storage/uploads')));
 
 // Health check endpoint
-app.get('/api/health', async (req, res) => {
+app.get('/health', async (req, res) => {
   try {
     // Check database connectivity
     await db.raw('SELECT 1');