refactor: simplify interfaces and improve configuration handling

- Removed unused ApiApp and ServerApp interfaces from core/apps/interfaces.go to streamline the codebase.
- Updated the GetApi method in the Server struct to return a pointer to the Api type for better type handling.
- Simplified the GetGinMode function in core/utils/config.go to always return gin.ReleaseMode, removing unnecessary conditional checks for development mode.
- These changes enhance code clarity and maintainability by eliminating redundant code and improving type safety.

core/utils/config.go

@@ -73,11 +73,7 @@ func GetGinMode() string {
 	if res := viper.GetString("gin.mode"); res != "" {
 		return res
 	}
-	if IsDev() {
-		return gin.DebugMode
-	} else {
-		return gin.ReleaseMode
-	}
+	return gin.ReleaseMode
 }
 
 func IsPro() bool {