Migrate CI workflow from GitHub Actions to Gitea Actions

Moves workflow to .gitea/workflows/ and updates container registry
from ghcr.io to git.necloud.us using REGISTRY_USER/REGISTRY_TOKEN secrets.

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

.gitea/workflows/publish-container.yml

@@ -0,0 +1,43 @@
+name: Publish Container
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: git.necloud.us
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Extract image metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: git.necloud.us/nate/weather
+          tags: |
+            type=raw,value=latest
+            type=sha
+
+      - name: Build and push image
+        uses: docker/build-push-action@v6
+        with:
+          context: ./app
+          file: ./app/Dockerfile
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}