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.

cmd/server/main.go

@@ -45,6 +45,25 @@ func main() {
 	gin.SetMode(gin.ReleaseMode)
 	router := gin.New()
 	router.Use(gin.Recovery())
+	// Add request logging middleware
+	router.Use(func(c *gin.Context) {
+		start := time.Now()
+		path := c.Request.URL.Path
+		raw := c.Request.URL.RawQuery
+
+		c.Next()
+
+		latency := time.Since(start)
+		clientIP := c.ClientIP()
+		method := c.Request.Method
+		statusCode := c.Writer.Status()
+
+		if raw != "" {
+			path = path + "?" + raw
+		}
+
+		log.Printf("[%s] %s %s %d %v", clientIP, method, path, statusCode, latency)
+	})
 
 	if len(cfg.TrustedProxies) > 0 {
 		router.SetTrustedProxies(cfg.TrustedProxies)
@@ -55,9 +74,16 @@ func main() {
 
 	webHandler := handlers.NewWebHandler(db, cfg)
 	dynHandler := handlers.NewDynDNSHandler(db, dnsClient, cfg)
+	debugHandler := handlers.NewDebugHandler(db, dnsClient, cfg)
 
 	router.GET("/", webHandler.Index)
 
+	// Debug/health endpoints (no rate limiting)
+	router.GET("/health", debugHandler.Health)
+	router.GET("/debug/config", debugHandler.ConfigDebug)
+	router.GET("/debug/stats", debugHandler.Stats)
+	router.GET("/debug/test-dns", debugHandler.TestDNS)
+
 	api := router.Group("/api")
 	api.Use(rateLimiter.RateLimitByIP())
 	{