perf: lazy-load mentionable users instead of preloading on app init

Remove the useEffect that preloads mentionable users on app mount.
The data is now fetched on-demand when:
- User types @ in the editor (MentionPerson component)
- User opens the share panel (SharePanel component)

This improves initial load performance and avoids potential race
conditions during OAuth login where the API might be called before
the token is fully recognized.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: appflowy

src/components/app/layers/AppBusinessLayer.tsx

@@ -229,11 +229,6 @@ export const AppBusinessLayer: React.FC<AppBusinessLayerProps> = ({ children })
     }
   }, [debouncedRefreshOutline, lastUpdatedCollab]);
 
-  // Load mentionable users on mount
-  useEffect(() => {
-    void loadMentionableUsers();
-  }, [loadMentionableUsers]);
-
   // Enhanced toView that uses loadViewMeta
   const enhancedToView = useCallback(
     async (viewId: string, blockId?: string, keepSearch?: boolean) => {