fix: resolve critical production deployment issues

- Fix database connection error "getaddrinfo ENOTFOUND postgres"
- Add wait-for-db.sh script to ensure PostgreSQL is ready before starting
- Fix email processor initialization timing issue
- Add missing storage path environment variables
- Add database dependency to backend service
- Enhance health check endpoint with database connectivity check
- Update production database defaults to match docker-compose
- Install postgresql-client in Docker image for health checks
- Document all required environment variables in .env.example

Fixes immediate production deployment failures and ensures proper service startup order.

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

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

backend/server.js

@@ -13,7 +13,7 @@ const path = require('path');
 const { initializeDatabase } = require('./src/database/db');
 const { startFileWatcher } = require('./src/services/fileWatcher');
 const { startExpirationChecker } = require('./src/services/expirationChecker');
-const { startEmailQueueProcessor } = require('./src/services/emailProcessor');
+const { initializeTransporter, startEmailQueueProcessor } = require('./src/services/emailProcessor');
 const { maintenanceMiddleware } = require('./src/middleware/maintenance');
 const { sessionTimeoutMiddleware } = require('./src/middleware/sessionTimeout');
 const logger = require('./src/utils/logger');
@@ -152,8 +152,25 @@ 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', (req, res) => {
-  res.json({ status: 'ok', timestamp: new Date().toISOString() });
+app.get('/api/health', async (req, res) => {
+  try {
+    // Check database connectivity
+    await db.raw('SELECT 1');
+    
+    res.json({ 
+      status: 'ok', 
+      database: 'connected',
+      timestamp: new Date().toISOString() 
+    });
+  } catch (error) {
+    logger.error('Health check failed:', error);
+    res.status(503).json({ 
+      status: 'error', 
+      database: 'disconnected',
+      error: error.message,
+      timestamp: new Date().toISOString() 
+    });
+  }
 });
 
 // Routes
@@ -189,7 +206,8 @@ async function startServer() {
     // Start expiration checker
     startExpirationChecker();
     
-    // Start email queue processor
+    // Initialize email transporter and start queue processor
+    await initializeTransporter();
     startEmailQueueProcessor();
     
     app.listen(PORT, () => {