Move frontend workflow to root .gitea/workflows

Gitea Actions only detects workflows at repo root, not subdirectories.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/build-frontend.yaml

@@ -0,0 +1,49 @@
+name: Build and Push Frontend Docker Image
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'frontend/**'
+      - '.gitea/workflows/build-frontend.yaml'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    container:
+      image: catthehacker/ubuntu:act-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Gitea Registry
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.voyager.sh
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: gitea.voyager.sh/nick/comfyui-frontend
+          tags: |
+            type=sha,prefix=
+            type=raw,value=latest
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: ./frontend
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max