ci: add GitHub Actions workflow for multi-arch Docker + releases

On tag push (v*):
- Creates a GitHub Release with auto-generated release notes
- Builds multi-arch Docker image (linux/amd64, linux/arm64)
- Pushes to ghcr.io/nesquena/hermes-webui with semver tags
- Uses GitHub Actions cache for faster builds

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/release.yml

@@ -0,0 +1,61 @@
+name: Release & Docker
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: write
+  packages: write
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      # Create GitHub Release from tag
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          generate_release_notes: true
+
+      # Set up multi-arch build
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
+
+      # Log in to GHCR
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Extract version tags (e.g. v0.19 -> 0.19, latest)
+      - 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}}
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      # Build and push multi-arch image
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max