Add GraalPy 25 image replacing CPython

Multi-stage Dockerfile.graalpy on ghcr.io/graalvm/graalpy-community:25
that builds the granian and rloop PyO3 extensions from source against
GraalPy (no GraalPy wheels exist), installs the pure-Python deps, and
serves the unchanged RSGI app on the rloop event loop.

Adds docker-compose.graalpy.yml and a CI job publishing the image as
the *-graalpy tags on release/*.

.gitea/workflows/build.yaml

@@ -36,3 +36,38 @@ jobs:
           push: true
           pull: true
           tags: ${{ steps.meta.outputs.tags }}
+
+  build_and_push_graalpy_docker_image:
+    name: "Build and push GraalPy docker image"
+    runs-on: hostinger
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v6
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Login to Gitea container registry
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.woggioni.net
+          username: woggioni-opencode-agent
+          password: ${{ secrets.PUBLISHER_TOKEN }}
+      - name: Extract metadata for GraalPy image tags
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: gitea.woggioni.net/woggioni/pyfconfig
+          flavor: |
+            latest=false
+            suffix=-graalpy
+          tags: |
+            type=match,pattern=release/(.*),group=1
+            type=raw,value=latest
+      - name: Build and push GraalPy docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: Dockerfile.graalpy
+          platforms: linux/amd64
+          push: true
+          pull: true
+          tags: ${{ steps.meta.outputs.tags }}