feat(image): KEY-WP-0002 T01/T02/T06 — Makefile image targets, Gitea Actions workflow, README CI docs

- Makefile: add IMAGE_REGISTRY/IMAGE_REPO/IMAGE_TAG vars + image, push, image-tag targets
- .gitea/workflows/image.yaml: build+push on main push and v* tags via metadata-action
- README: Container Image section with pull/build/push/CI secret docs

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

.gitea/workflows/image.yaml

@@ -0,0 +1,51 @@
+name: Build and Publish Container Image
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - "v*"
+
+env:
+  REGISTRY: 92.205.130.254:32166
+  IMAGE_NAME: netkingdom/key-cape
+
+jobs:
+  build-and-push:
+    runs-on: act_runner
+    steps:
+      - name: Checkout
+        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: ${{ env.REGISTRY }}
+          username: ${{ secrets.REGISTRY_USER }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=sha,prefix=main-,format=short,enable={{is_default_branch}}
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max