Add comprehensive logging and debug endpoints for production troubleshooting

- Add request logging middleware to main.go
- Add debug handler with health, config, stats, and test-dns endpoints
- Add detailed logging to DynDNS handler
- Add logging to Technitium DNS client
- Add database Ping() and GetStats() methods
- New endpoints:
  - /health - detailed health status with database and DNS checks
  - /debug/config - sanitized configuration
  - /debug/stats - database statistics
  - /debug/test-dns - live DNS test endpoint

This will help diagnose production issues with DNS updates.

internal/database/db.go

@@ -54,6 +54,42 @@ func (db *DB) Close() error {
 	return db.conn.Close()
 }
 
+// Ping checks if the database connection is alive
+func (db *DB) Ping() error {
+	return db.conn.Ping()
+}
+
+// GetStats returns database statistics
+func (db *DB) GetStats() (map[string]interface{}, error) {
+	stats := make(map[string]interface{})
+
+	// Get total spaces count
+	var totalSpaces int
+	err := db.conn.QueryRow("SELECT COUNT(*) FROM spaces").Scan(&totalSpaces)
+	if err != nil {
+		return nil, err
+	}
+	stats["total_spaces"] = totalSpaces
+
+	// Get spaces with IPs (active)
+	var activeSpaces int
+	err = db.conn.QueryRow("SELECT COUNT(*) FROM spaces WHERE last_ip IS NOT NULL").Scan(&activeSpaces)
+	if err != nil {
+		return nil, err
+	}
+	stats["active_spaces"] = activeSpaces
+
+	// Get recently updated (last 24 hours)
+	var recentlyUpdated int
+	err = db.conn.QueryRow("SELECT COUNT(*) FROM spaces WHERE updated_at > datetime('now', '-1 day')").Scan(&recentlyUpdated)
+	if err != nil {
+		return nil, err
+	}
+	stats["recently_updated_24h"] = recentlyUpdated
+
+	return stats, nil
+}
+
 func (db *DB) CreateSpace(ctx context.Context, subdomain string) (*models.Space, error) {
 	token, err := generateToken()
 	if err != nil {