fix: improve email processor reliability and add diagnostic tools

- Enhanced email processor with comprehensive logging
- Added error handling for database queries in email processing
- Fixed duplicate export in module.exports
- Added testEmailConnection() function for connectivity testing
- Created diagnostic scripts:
  - check-email-processor.js: Full diagnostic with manual processing
  - run-email-processor.js: Standalone processor (can run once or continuously)
  - check-email-environment.js: Environment and configuration checker
- Fixed missing translation: added 'common.unknown' in EN/DE locales

This should help identify why emails aren't being processed on production.

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

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

backend/scripts/run-email-processor.js

@@ -0,0 +1,111 @@
+#!/usr/bin/env node
+
+const { db } = require('../src/database/db');
+const { 
+  initializeTransporter, 
+  processEmailQueue, 
+  testEmailConnection 
+} = require('../src/services/emailProcessor');
+const winston = require('winston');
+
+// Create a simple console logger
+const logger = winston.createLogger({
+  format: winston.format.simple(),
+  transports: [new winston.transports.Console()]
+});
+
+async function runEmailProcessor(runOnce = false) {
+  try {
+    logger.info('=== Starting Email Processor ===\n');
+    
+    // Initialize transporter
+    logger.info('Initializing email transporter...');
+    await initializeTransporter();
+    
+    // Test connection
+    logger.info('Testing email connection...');
+    const connectionOk = await testEmailConnection();
+    
+    if (!connectionOk) {
+      logger.error('Email connection test failed! Check your SMTP configuration.');
+      logger.info('\nRequired environment variables:');
+      logger.info('- SMTP_HOST');
+      logger.info('- SMTP_PORT');
+      logger.info('- SMTP_USER');
+      logger.info('- SMTP_PASS');
+      logger.info('- SMTP_FROM');
+      process.exit(1);
+    }
+    
+    logger.info('Email connection test successful!\n');
+    
+    if (runOnce) {
+      // Process queue once
+      logger.info('Processing email queue once...');
+      await processEmailQueue();
+      logger.info('Email processing complete');
+      
+      // Show final status
+      const pendingCount = await db('email_queue')
+        .where('status', 'pending')
+        .where('retry_count', '<', 3)
+        .count('* as count')
+        .first();
+      
+      logger.info(`\nEmails still pending: ${pendingCount.count}`);
+      
+      await db.destroy();
+      process.exit(0);
+    } else {
+      // Run continuously
+      logger.info('Starting continuous email processor...');
+      logger.info('Processing emails every 60 seconds. Press Ctrl+C to stop.\n');
+      
+      // Process immediately
+      await processEmailQueue();
+      
+      // Then every minute
+      setInterval(async () => {
+        try {
+          await processEmailQueue();
+        } catch (error) {
+          logger.error('Error processing email queue:', error);
+        }
+      }, 60000);
+    }
+    
+  } catch (error) {
+    logger.error('Fatal error:', error);
+    await db.destroy();
+    process.exit(1);
+  }
+}
+
+// Handle graceful shutdown
+process.on('SIGINT', async () => {
+  logger.info('\n\nShutting down email processor...');
+  await db.destroy();
+  process.exit(0);
+});
+
+// Check command line arguments
+const args = process.argv.slice(2);
+const runOnce = args.includes('--once') || args.includes('-o');
+
+if (args.includes('--help') || args.includes('-h')) {
+  console.log(`
+Email Processor Runner
+
+Usage: node run-email-processor.js [options]
+
+Options:
+  --once, -o     Process the email queue once and exit
+  --help, -h     Show this help message
+
+By default, the processor runs continuously, checking for emails every 60 seconds.
+  `);
+  process.exit(0);
+}
+
+// Run the processor
+runEmailProcessor(runOnce);