refactor: Clean up logging system with LOG_LEVEL filtering

- Add LOG_LEVEL env variable support (debug, info, warn, error)
- Default to 'info' level for production-ready logs
- Integrate Morgan HTTP logging with custom logger
- Remove console.logs and replace with custom logger
- Remove sensitive password debug logs from email service
- Remove noisy warn logs from email sync and event notifier
- Add gray color for timestamps to improve readability

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/config/database.js

@@ -15,9 +15,9 @@ const pool = new Pool({
   connectionTimeoutMillis: 2000,
 });
 
-// Note: Connection logging handled in index.js to avoid circular dependencies
+// Critical database errors - use console.error directly to avoid circular imports
 pool.on('error', (err) => {
-  console.error('Neočakávaná chyba databázy:', err);
+  console.error('[FATAL] Database connection error:', err.message);
   process.exit(-1);
 });