refactor: rename project DADA → 云梦 (slug: yume)

- 所有 workspace 包 @dada/* → @yume/*，根包 dada → yume
- 全部导入路径同步更新
- 内部 ID 对齐：dada-ripple → yume-ripple，dada:custom → yume:custom
- 首页 / new / play 用户文案整段中文化，保留 smallcaps + 衬线 + 罗马数字排版语汇
- README 标题改为 "# 云梦"，部署链接与目录树 slug 改为 yume
- 重新生成 pnpm-lock.yaml

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/api/start/route.ts

@@ -1,5 +1,5 @@
-import { startSession } from "@dada/engine";
-import type { StartRequest } from "@dada/types";
+import { startSession } from "@yume/engine";
+import type { StartRequest } from "@yume/types";
 import { NextResponse } from "next/server";
 import { loadEngineConfig } from "@/lib/config";