feat: Add public user information retrieval endpoint

- Introduced a new endpoint to fetch public user information without authentication.
- Implemented UserToPublicUserInfo function to format user data for the response.
- Updated UserService interface and user service implementation to support fetching users by username.
- Enhanced user handler to validate input parameters and check user status before responding.

cmd/server/main.go

@@ -32,6 +32,8 @@ import (
 
 	"github.com/gin-gonic/gin"
 	"go.uber.org/zap"
+
+	_ "carrotskin/docs"
 )
 
 func main() {