ci: publish Docker image to GHCR on every main push

.github/workflows/ci.yml

@@ -32,8 +32,24 @@ jobs:
     needs: test
     runs-on: ubuntu-latest
     if: github.ref == 'refs/heads/main'
+    permissions:
+      contents: read
+      packages: write
     steps:
       - uses: actions/checkout@v4
 
-      - name: Build Docker image
-        run: docker build -t ai-code-review-agent:${{ github.sha }} .
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: |
+            ghcr.io/${{ github.repository }}:latest
+            ghcr.io/${{ github.repository }}:${{ github.sha }}