refactor(navigation): consolidate navigation with href helpers and extract push device hook

- Migrate all navigation calls from magic strings to centralized href helpers
- Extract inline device registration logic into useRegisterPushDevice hook
- Remove unused terms and privacy policy routes from profile stack
- Add hrefTradeDetail helper for trade detail navigation
- Restore routePayloadCache.stashSystemMessage for group request/invite handling
- Change desktop shell tab navigation from replace to push

src/components/business/PostRefCard.tsx

@@ -6,6 +6,7 @@ import { useRouter } from 'expo-router';
 import Text from '../common/Text';
 import { useAppColors, spacing, borderRadius } from '../../theme';
 import type { PostRefSegmentData } from '../../types';
+import * as hrefs from '../../navigation/hrefs';
 
 interface PostRefCardProps {
   data: PostRefSegmentData;
@@ -21,7 +22,7 @@ const PostRefCard: React.FC<PostRefCardProps> = ({ data, compact = false, onPres
     if (onPress) {
       onPress(data.post_id);
     } else {
-      router.push(`/post/${data.post_id}` as any);
+      router.push(hrefs.hrefPostDetail(data.post_id));
     }
   }, [data.post_id, onPress, router]);