Refactor handlers and update changelog for 5.0.0-Beta

- Split IndexHandler into HealthHandler, VersionHandler, and CharacterHandler
- Rename index.go to version.go in backend
- Change VersionData.Changelog from string to []string
- Add changelog entries for issues #16-#23
- Remove TestDB function and related code
- Fix import ordering in several files

Closes #21, #22
References #16, #17, #18, #19, #20, #23

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

internal/server/routes.go

@@ -10,8 +10,8 @@ import (
 	"github.com/labstack/echo/v5"
 	"github.com/labstack/echo/v5/middleware"
 	echoSwagger "github.com/swaggo/echo-swagger/v2"
-	"music-server/internal/logging"
 	"go.uber.org/zap"
+	"music-server/internal/logging"
 )
 
 //	@Title			MusicServer API
@@ -29,7 +29,7 @@ import (
 // @BasePath	/
 func (s *Server) RegisterRoutes() http.Handler {
 	e := echo.New()
-	
+
 	// Serve OpenAPI spec at /openapi
 	e.GET("/openapi", echo.WrapHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
@@ -57,12 +57,16 @@ func (s *Server) RegisterRoutes() http.Handler {
 	// Swagger UI
 	e.GET("/swagger/*", echoSwagger.WrapHandler)
 
-	index := NewIndexHandler()
-	e.GET("/version", index.GetVersion)
-	e.GET("/dbtest", index.GetDBTest)
-	e.GET("/health", index.HealthCheck)
-	e.GET("/character", index.GetCharacter)
-	e.GET("/characters", index.GetCharacterList)
+	health := NewHealthHandler()
+	e.GET("/health", health.HealthCheck)
+
+	version := NewVersionHandler()
+	e.GET("/version", version.GetLatestVersion)
+	e.GET("/version/history", version.GetVersionHistory)
+
+	character := NewCharacterHandler()
+	e.GET("/character", character.GetCharacter)
+	e.GET("/characters", character.GetCharacterList)
 
 	download := NewDownloadHandler()
 	e.GET("/download", download.checkLatest)