feat: health check for backend in docker-compose;

feat: go dockerfile preinstalls curl;
refactor: reduced go image size by using a 2 stage dockerfile;
refactor: switch frontend dockerfile

backend/internal/controllers/service.go

@@ -7,5 +7,5 @@ import (
 )
 
 func HealthCheck(c *gin.Context) {
-	c.JSON(http.StatusOK, gin.H{"status": "ok"})
+	c.JSON(http.StatusOK, gin.H{"healthy": true})
 }