ci: migrate workflows from GitHub Actions to Gitea Actions

- Move CI workflow from .github/workflows/ to .gitea/workflows/
- Add Gitea Actions release workflow for tag builds
- Remove GitHub-specific release workflow

.gitea/workflows/release.yml

@@ -0,0 +1,20 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Build Docker image
+        run: docker build ./backend --tag aoc-backend:${{ gitea.ref_name }}
+
+      - name: Verify image exists
+        run: docker images | grep aoc-backend

.github/workflows/release.yml

@@ -1,55 +0,0 @@
-name: Release
-
-on:
-  push:
-    tags:
-      - "v*"
-
-env:
-  REGISTRY: ghcr.io
-  IMAGE_NAME: ${{ github.repository }}-backend
-
-jobs:
-  build-and-push:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: read
-      packages: write
-      attestations: write
-      id-token: write
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
-      - name: Log in to Container Registry
-        uses: docker/login-action@v3
-        with:
-          registry: ${{ env.REGISTRY }}
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Extract metadata
-        id: meta
-        uses: docker/metadata-action@v5
-        with:
-          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
-          tags: |
-            type=semver,pattern={{version}}
-            type=semver,pattern={{major}}.{{minor}}
-
-      - name: Build and push Docker image
-        id: push
-        uses: docker/build-push-action@v6
-        with:
-          context: ./backend
-          push: true
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-
-      - name: Generate artifact attestation
-        uses: actions/attest-build-provenance@v1
-        with:
-          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
-          subject-digest: ${{ steps.push.outputs.digest }}
-          push-to-registry: true