Add Gitea Actions workflow to build and push Docker image

Triggers on push to main. Uses BuildKit registry cache so the expensive
CTranslate2 HIP compilation is cached between runs. Pushes both :latest
and :<sha> tags to git.sdgarren.com container registry.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -0,0 +1,34 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to registry
+        uses: docker/login-action@v3
+        with:
+          registry: git.sdgarren.com
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: |
+            git.sdgarren.com/scott/rocm-faster-whisper:latest
+            git.sdgarren.com/scott/rocm-faster-whisper:${{ gitea.sha }}
+          cache-from: type=registry,ref=git.sdgarren.com/scott/rocm-faster-whisper:buildcache
+          cache-to: type=registry,ref=git.sdgarren.com/scott/rocm-faster-whisper:buildcache,mode=max