docs: architecture, permissions, admin guide + refresh schema/workflows

- New ARCHITECTURE.md (3-layer model + data flow + lifecycle matrix)
- New PERMISSIONS.md (grant calculation rules + enforcement)
- New ADMIN_GUIDE.md (華文极简：Customer/CustomerProduct 授权 + Product/Resource 管理)
- Rewrite N8N_WORKFLOWS.md from WF1-6 (obsolete) to actual W1/W2/W3
- Update DATABASE_SCHEMA.md: fix status enum (drop 'disabled'), add 5-status semantics
- Update README.md doc index

README.md

@@ -35,6 +35,9 @@ alist-serve-resource/
 ├── .gitignore
 ├── docs/
 │   ├── API_INTEGRATION.md  # ★ AList API 源码级验证
+│   ├── ARCHITECTURE.md     # 三层职责与数据流
+│   ├── PERMISSIONS.md      # 权限计算规则
+│   ├── ADMIN_GUIDE.md      # ★ 管理员操作指南（华文，极简）
 │   ├── INSTALL.md
 │   ├── CONFIGURATION.md
 │   ├── DATABASE_SCHEMA.md