ci: add Docker CI workflows and switch to pre-built image

- Add GitHub Actions workflow to build and push Docker image to GitHub Container Registry
- Add Gitea workflow for building and pushing Docker image to private registry
- Update docker-compose.yml to use pre-built image instead of local build

docker-compose.yml

@@ -2,8 +2,7 @@ version: '3.8'
 
 services:
   calorie-tracker:
-    build: 
-      context: ./calorie_tracker_app
+    image: 192.168.100.105:3002/kingjaypee12/calorie-tracker:latest
     container_name: calorie-tracker
     restart: unless-stopped
     ports: