Replace Axios with native fetch; add global 401 session-expiry redirect

All API calls now go through a thin request() wrapper around native fetch.
Removes the axios dependency entirely. The wrapper injects the JWT on every
request and — the key fix — clears localStorage and redirects to /login on
any 401 response, so expired sessions no longer leave users on broken pages.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/STATUS.md

@@ -130,6 +130,8 @@ Display and edit personal information.
 
 ## API client (`src/api/client.ts`)
 
+**No Axios** — replaced with a native `fetch` wrapper (`request()`). Global 401 handler clears the token and redirects to `/login`, fixing the expired-session blank-page bug. All exported function signatures are unchanged.
+
 Key document-related functions:
 
 | Function | Description |
@@ -199,6 +201,7 @@ Key document-related functions:
 - [x] Document sharing UI (Sharing section + Shared with me view)
 - [x] AI suggestion confirm/reject UI (folder + filename)
 - [x] Groups admin UI
+- [x] Replace Axios with native fetch; add global 401 → `/login` redirect for expired sessions
 - [ ] Toast notification system
 - [ ] Loading skeletons
 - [ ] Cmd+K global search (`CommandDialog`)