refactor: Flatten directory structure

Move project files from uzdb/ subdirectory to root directory for cleaner project structure.

Changes:
- Move frontend/ to root
- Move internal/ to root
- Move build/ to root
- Move all config files (go.mod, wails.json, etc.) to root
- Remove redundant uzdb/ subdirectory nesting

Project structure is now:
├── frontend/        # React application
├── internal/        # Go backend
├── build/           # Wails build assets
├── doc/             # Design documentation
├── main.go          # Entry point
└── ...

🤖 Generated with Qoder

internal/handler/server.go

@@ -0,0 +1,95 @@
+package handler
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"go.uber.org/zap"
+
+	"uzdb/internal/config"
+	"uzdb/internal/middleware"
+	"uzdb/internal/services"
+)
+
+// HTTPServer represents the HTTP API server
+type HTTPServer struct {
+	engine *gin.Engine
+	server *http.Server
+}
+
+// NewHTTPServer creates a new HTTP server
+func NewHTTPServer(
+	connectionSvc *services.ConnectionService,
+	querySvc *services.QueryService,
+) *HTTPServer {
+	// Set Gin mode based on environment
+	cfg := config.Get()
+	if cfg.IsProduction() {
+		gin.SetMode(gin.ReleaseMode)
+	}
+
+	engine := gin.New()
+
+	// Create handlers
+	connectionHandler := NewConnectionHandler(connectionSvc)
+	queryHandler := NewQueryHandler(connectionSvc, querySvc)
+
+	// Setup middleware
+	engine.Use(middleware.RecoveryMiddleware())
+	engine.Use(middleware.LoggerMiddleware())
+	engine.Use(middleware.CORSMiddleware())
+	engine.Use(middleware.SecureHeadersMiddleware())
+
+	// Setup routes
+	api := engine.Group("/api")
+	{
+		connectionHandler.RegisterRoutes(api)
+		queryHandler.RegisterRoutes(api)
+	}
+
+	// Health check endpoint
+	engine.GET("/health", func(c *gin.Context) {
+		c.JSON(http.StatusOK, gin.H{
+			"status":    "ok",
+			"timestamp": time.Now().Format(time.RFC3339),
+		})
+	})
+
+	return &HTTPServer{
+		engine: engine,
+	}
+}
+
+// Start starts the HTTP server
+func (s *HTTPServer) Start(port string) error {
+	s.server = &http.Server{
+		Addr:         ":" + port,
+		Handler:      s.engine,
+		ReadTimeout:  15 * time.Second,
+		WriteTimeout: 15 * time.Second,
+		IdleTimeout:  60 * time.Second,
+	}
+
+	config.GetLogger().Info("starting HTTP API server",
+		zap.String("port", port))
+
+	if err := s.server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+		return fmt.Errorf("failed to start HTTP server: %w", err)
+	}
+
+	return nil
+}
+
+// Shutdown gracefully shuts down the HTTP server
+func (s *HTTPServer) Shutdown(ctx context.Context) error {
+	if s.server == nil {
+		return nil
+	}
+
+	config.GetLogger().Info("shutting down HTTP server")
+
+	return s.server.Shutdown(ctx)
+}