Add Docker build with Gitea Actions CI

- Add Dockerfile with Python 3.13 + uv
- Add Gitea Actions workflow for auto-build on push
- Add deposit_api.py for balance management
- Update api_server.py with domain registration endpoint

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

.gitea/workflows/docker.yaml

@@ -0,0 +1,51 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - master
+      - main
+    tags:
+      - 'v*'
+
+env:
+  REGISTRY: ${{ gitea.server_url }}
+  IMAGE_NAME: ${{ gitea.repository }}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ gitea.actor }}
+          password: ${{ secrets.GITEA_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=sha,prefix=
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max