chore: initial commit of sso-mock SSO login service

Next.js + Mantine mock SSO service providing account/password, phone
verify-code, and Feishu QR login. Issues a one-time sso_code that the
external app exchanges for user info.

Includes:
- Feishu callback fix: guard against duplicate/concurrent /api/login
  submissions of the same single-use authorization code (feishuLogin
  once-guard + memoized onLoginSuccess to stop effect re-fire).
- ADAPTATION_GUIDE.md: how to switch from the in-memory code store to
  the real backend auth/index + inner_get_user_info endpoints.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

utils/code-store.ts

@@ -0,0 +1,41 @@
+/**
+ * Mock SSO 认证码存储（内存）
+ * 生产环境应使用 Redis 等持久化方案
+ */
+
+interface MockUser {
+  id: string
+  account: string
+  name: string
+  phone: string
+  avatar: string
+  roles: string[]
+}
+
+interface CodeEntry {
+  user: MockUser
+  expires: number
+}
+
+// 使用 globalThis 避免 Next.js 开发模式下 HMR 导致数据丢失
+const globalForCodeStore = globalThis as unknown as {
+  __ssoCodeStore: Map<string, CodeEntry> | undefined
+}
+
+if (!globalForCodeStore.__ssoCodeStore) {
+  globalForCodeStore.__ssoCodeStore = new Map()
+}
+
+export const codeStore = globalForCodeStore.__ssoCodeStore!
+
+// 定时清理过期 code（仅在非 edge 环境）
+if (typeof setInterval !== 'undefined') {
+  setInterval(() => {
+    const now = Date.now()
+    for (const [key, val] of codeStore) {
+      if (val.expires < now) codeStore.delete(key)
+    }
+  }, 60_000)
+}
+
+export type { MockUser, CodeEntry }