docs: freeze YuXinGu lexicon, journey, and P1 engineering sources

Establish product language contract, user journey with dual growth engines,
ERD/OpenAPI/Go boundaries, and H5 routes (/profile, /portrait, /relation,
/membership) before P1 implementation.

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

apps/user-h5/src/components/TabBar.vue

@@ -20,7 +20,7 @@ const route = useRoute()
 const items = [
   { to: '/', icon: '⌂', label: '首页' },
   { to: '/explore', icon: '◎', label: '探索' },
-  { to: '/ask', icon: '问', label: '问', ask: true },
+  { to: '/ask', icon: '问', label: '问答', ask: true },
   { to: '/companion', icon: '♡', label: '陪伴' },
   { to: '/mine', icon: '◍', label: '我的' },
 ]