feat(miniapp): add privacy consent and legal pages

Show privacy popup on launch, gate login on legal consent, and link
user agreement and privacy policy pages in the mini program.

Co-authored-by: Cursor <cursoragent@cursor.com>

miniapp/app.json

@@ -4,8 +4,12 @@
     "pages/chat/index",
     "pages/sessions/index",
     "pages/space/index",
-    "pages/webview/index"
+    "pages/webview/index",
+    "pages/legal/index/index",
+    "pages/legal/privacy/index",
+    "pages/legal/terms/index"
   ],
+  "__usePrivacyCheck__": true,
   "window": {
     "navigationBarTitleText": "TKMind",
     "navigationBarBackgroundColor": "#101820",