add Dockerfile + docker-compose: single-image deploy (nginx + backend)

Multi-stage build: node builds frontend dist, golang builds static
binary (modernc sqlite, CGO off), alpine runtime runs nginx :80 +
backend :8890 in one container. nginx serves SPA with fallback, strips
/api prefix (same as vite dev proxy), proxies protocol endpoints
(/mcp, /m/*, /v1/*, /d/*, /ws/*, *.php) with buffering off for
NDJSON/SSE streams and WS upgrade headers.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

docker-compose.yml

@@ -0,0 +1,17 @@
+services:
+  cyibox:
+    build: .
+    image: cyi-box:latest
+    container_name: cyibox
+    ports:
+      - "8890:80"          # 对外端口，左侧可改成任意宿主端口
+    volumes:
+      - cyibox-data:/app/data   # SQLite + vault.key + 网盘文件都落这里
+    environment:
+      CYIBOX_ADMIN_PASSWORD: ${CYIBOX_ADMIN_PASSWORD:-admin123}   # 首启种子管理员密码，建议改
+      # CYIBOX_ADMIN_NAME: admin
+      # CYIBOX_CORS: "https://a.com,https://b.com"
+    restart: unless-stopped
+
+volumes:
+  cyibox-data: