docs: add frontend handoff architecture and index

docs/index.md

@@ -0,0 +1,17 @@
+# member docs index
+
+## 先看這三份
+1. `docs/FRONTEND_ARCHITECTURE.md`
+2. `docs/FRONTEND_API_CONTRACT.md`
+3. `docs/FRONTEND_IMPLEMENTATION_CHECKLIST.md`
+
+## 系統架構與後端
+- `docs/ARCHITECTURE_AND_CONFIG.md`
+- `docs/BACKEND_ARCHITECTURE.md`
+- `docs/BACKEND_BOOTSTRAP.md`
+
+## SQL 與配置
+- `docs/API_CLIENTS_SQL.sql`
+
+## 給前端 AI 的一句話交接
+請先完成 `/me`、`/me/permissions/snapshot`、`/admin/permissions/grant|revoke` 三組 API 對接，並依 `FRONTEND_IMPLEMENTATION_CHECKLIST.md` 逐項完成。