ci: add Dockerfile and Gitea Actions workflow for automated image builds

- Dockerfile based on node:18-alpine
- Gitea Actions workflow triggers on push to release/* branches
- Builds and pushes to Gitea container registry with version tags

.gitea/workflows/build-image.yml

@@ -0,0 +1,40 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - 'release/**'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Extract version from package.json
+        id: version
+        run: |
+          VERSION=$(node -p "require('./package.json').version")
+          BRANCH=${GITHUB_REF#refs/heads/}
+          RELEASE_NAME=${BRANCH#release/}
+          echo "version=${VERSION}" >> $GITHUB_OUTPUT
+          echo "release=${RELEASE_NAME}" >> $GITHUB_OUTPUT
+          echo "Building version ${VERSION} from branch ${BRANCH}"
+
+      - name: Login to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: git.i3omb.com
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_PASSWORD }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: |
+            git.i3omb.com/gandalf/sofarr:${{ steps.version.outputs.version }}
+            git.i3omb.com/gandalf/sofarr:${{ steps.version.outputs.release }}
+            git.i3omb.com/gandalf/sofarr:latest