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

.gitea/workflows/docker.yml

@@ -0,0 +1,41 @@
+name: Build and Push Docker Image (Gitea)
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - 'v*.*.*'
+  workflow_dispatch:
+permissions:
+  contents: read
+  packages: write
+env:
+  REGISTRY: 192.168.100.105:3002
+  IMAGE_NAME: calorie-tracker
+  IMAGE_ID: ${{ env.REGISTRY }}/${{ github.repository_owner }}/${{ env.IMAGE_NAME }}
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ secrets.CR_USERNAME }}
+          password: ${{ secrets.CR_PASSWORD }}
+      - id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.IMAGE_ID }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=ref,event=tag
+            type=sha
+      - uses: docker/build-push-action@v5
+        with:
+          context: ./calorie_tracker_app
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}