feat: add Gitea Actions workflow for Docker builds

Add Gitea Actions workflow to automatically build and push Docker
images to Gitea container registry.

New files:
- .gitea/workflows/build.yaml: Automated Docker build workflow
  - Triggers on push to main, tags, and manual dispatch
  - Builds Docker image from Dockerfile
  - Tags appropriately (commit SHA, tags, latest)
  - Pushes to Gitea registry at 10.0.1.10

- CONTAINER_REGISTRY.md: Complete documentation for:
  - Enabling Gitea container registry
  - Setting up CI/CD with Gitea Actions
  - Creating and using personal access tokens
  - Pulling and pushing images
  - Troubleshooting common issues

The workflow is compatible with the existing Dockerfile and provides
automated builds similar to the GitLab CI pipeline.

Prerequisites:
- Gitea container registry enabled
- GITEA_TOKEN secret configured with write:package scope

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

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

.gitea/workflows/build.yaml

@@ -0,0 +1,77 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - '*'
+  workflow_dispatch:
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Determine image tags
+        id: tags
+        run: |
+          REGISTRY="10.0.1.10"
+          REPO_OWNER="${{ gitea.repository_owner }}"
+          REPO_NAME="${{ gitea.repository }}"
+
+          # Extract repository name without owner
+          REPO_NAME_ONLY=$(echo "$REPO_NAME" | cut -d'/' -f2)
+
+          # Base image path
+          IMAGE_BASE="${REGISTRY}/${REPO_OWNER}/${REPO_NAME_ONLY}"
+
+          # Determine tag based on ref
+          if [[ "${{ gitea.ref }}" == refs/tags/* ]]; then
+            # Tag push - use the tag name
+            TAG_NAME="${{ gitea.ref_name }}"
+            echo "IMAGE_TAG=${IMAGE_BASE}:${TAG_NAME}" >> $GITHUB_OUTPUT
+            echo "PUSH_LATEST=true" >> $GITHUB_OUTPUT
+          elif [[ "${{ gitea.ref_name }}" == "main" ]]; then
+            # Main branch - use commit SHA and latest
+            echo "IMAGE_TAG=${IMAGE_BASE}:${{ gitea.sha_short }}" >> $GITHUB_OUTPUT
+            echo "PUSH_LATEST=true" >> $GITHUB_OUTPUT
+          else
+            # Other branches - use branch name
+            BRANCH_TAG=$(echo "${{ gitea.ref_name }}" | sed 's/\//-/g')
+            echo "IMAGE_TAG=${IMAGE_BASE}:${BRANCH_TAG}" >> $GITHUB_OUTPUT
+            echo "PUSH_LATEST=false" >> $GITHUB_OUTPUT
+          fi
+
+          echo "IMAGE_LATEST=${IMAGE_BASE}:latest" >> $GITHUB_OUTPUT
+
+      - name: Log in to Gitea Container Registry
+        run: |
+          echo "${{ secrets.GITEA_TOKEN }}" | docker login 10.0.1.10 -u "${{ gitea.actor }}" --password-stdin
+
+      - name: Build Docker image
+        run: |
+          echo "Building Docker image..."
+          if [[ "${{ steps.tags.outputs.PUSH_LATEST }}" == "true" ]]; then
+            docker build -t ${{ steps.tags.outputs.IMAGE_TAG }} -t ${{ steps.tags.outputs.IMAGE_LATEST }} .
+          else
+            docker build -t ${{ steps.tags.outputs.IMAGE_TAG }} .
+          fi
+
+      - name: Push Docker image
+        run: |
+          echo "Pushing Docker image to registry..."
+          docker push ${{ steps.tags.outputs.IMAGE_TAG }}
+
+          if [[ "${{ steps.tags.outputs.PUSH_LATEST }}" == "true" ]]; then
+            echo "Pushing latest tag..."
+            docker push ${{ steps.tags.outputs.IMAGE_LATEST }}
+          fi
+
+          echo "Build and push completed successfully!"
+          echo "Image available at ${{ steps.tags.outputs.IMAGE_TAG }}"