feat(server): 单域托管 client/dist 与 SPA 回退（E12）

- 新增 SERVE_CLIENT_DIST/CLIENT_DIST_DIR 配置
- 开启后注册 @fastify/static 并对非 /api GET(html) 回退 index.html
- docker-compose.yml 与 README 补充用法

server/src/config.js

@@ -14,6 +14,7 @@ function getConfig() {
   const nodeEnv = process.env.NODE_ENV ?? "development";
   const serverRoot = path.resolve(__dirname, "..");
   const storageDir = process.env.STORAGE_DIR ?? "generated/storage";
+  const clientDistDir = process.env.CLIENT_DIST_DIR ?? "../client/dist";
 
   return {
     nodeEnv,
@@ -40,6 +41,8 @@ function getConfig() {
 
     appTimezone: process.env.APP_TIMEZONE ?? "Asia/Shanghai",
     storageDir: path.resolve(serverRoot, storageDir),
+    serveClientDist: process.env.SERVE_CLIENT_DIST === "true",
+    clientDistDir: path.resolve(serverRoot, clientDistDir),
     signedUrlTtlSeconds: Number(process.env.SIGNED_URL_TTL_SECONDS ?? 600),
     maxUploadSizeBytes: Number(process.env.MAX_UPLOAD_SIZE_BYTES ?? 10 * 1024 * 1024),