refactor(server): update main entry point and docs for Echo v5

Update cmd/server/main.go and internal/docs/http_handler.go for Echo v5.

Changes in main.go:
- Update import from echo/v4 to echo/v5
- Replace echomiddleware.Logger() with RequestLogger()
- Remove net/http import (no longer needed)
- Update server startup to use app.StartServer()
  - Replaces direct echo.Start() call
  - Better separation of concerns

Changes in http_handler.go:
- Update handler signatures to use *echo.Context
- Ensure Echo v5 compatibility

These changes complete the server layer migration to Echo v5.

cmd/server/main.go

@@ -12,13 +12,12 @@ import (
 	"bookhoard/internal/sync"
 	"context"
 	"log"
-	"net/http"
 	"time"
 
 	"github.com/go-playground/validator/v10"
 	"github.com/jackc/pgx/v5/pgxpool"
-	"github.com/labstack/echo/v4"
-	echomiddleware "github.com/labstack/echo/v4/middleware"
+	"github.com/labstack/echo/v5"
+	echomiddleware "github.com/labstack/echo/v5/middleware"
 )
 
 // CustomValidator wraps the go-playground validator
@@ -139,7 +138,7 @@ func main() {
 	e.Validator = &CustomValidator{validator: v}
 
 	// Middleware
-	e.Use(echomiddleware.Logger())
+	e.Use(echomiddleware.RequestLogger())
 	e.Use(echomiddleware.Recover())
 	e.Use(echomiddleware.CORS())
 	e.Use(ratelimit.RequestTracingMiddleware(cfg))
@@ -197,17 +196,14 @@ func main() {
 	// ========================================================================
 	// START SERVER (managed by app lifecycle)
 	// ========================================================================
-
 	log.Printf("Starting server on port %s", cfg.ServerPort)
 
-	// Start HTTP server in background
-	go func() {
-		if err := e.Start(":" + cfg.ServerPort); err != nil && err != http.ErrServerClosed {
-			log.Fatalf("Server failed to start: %v", err)
-		}
-	}()
+	// Start HTTP server
+	if err := application.StartServer(":" + cfg.ServerPort); err != nil {
+		log.Fatalf("Failed to start server: %v", err)
+	}
 
-	// Start application (blocks until shutdown signal)
+	// Start application lifecycle (blocks until shutdown signal)
 	if err := application.Start(); err != nil {
 		log.Fatalf("Application error: %v", err)
 	}