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.

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docker/entrypoint.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+
+# 后端跑在容器内 8890，nginx 对外 80（托管前端 + 反代 API/协议端点）
+/app/cyibox &
+API_PID=$!
+
+trap 'kill -TERM $API_PID 2>/dev/null' TERM INT
+
+nginx -g 'daemon off;' &
+NGINX_PID=$!
+
+wait $NGINX_PID
+kill -TERM $API_PID 2>/dev/null || true
+wait $API_PID 2>/dev/null || true