[AZ-510] Auth bootstrap: POST refresh + chained /users/me

Replace the broken `GET /api/admin/auth/refresh` (no `credentials:'include'`)
mount-time bootstrap with `POST /api/admin/auth/refresh` (with credentials)
chained to `GET /api/admin/users/me`. Returning users with a valid HttpOnly
refresh cookie no longer flash through `/login`. Closes Finding B3 / Vision P3.

- Add module-scoped `bootstrapInflight` guard (StrictMode double-mount safety)
  + test-only reset hook exported via the `src/auth` barrel; `tests/setup.ts`
  resets it in `afterEach` to prevent pending-promise leakage between tests.
- Defensive `hasPermission` against legacy `/users/me` payloads omitting
  `permissions`; default MSW handler now seeds `permissions` explicitly.
- Add `endpoints.admin.usersMe()` builder (STC-ARCH-02 forbids the literal).
- Bulk-swap 15 test files from `http.get` -> `http.post` for the refresh
  override so intentional bootstrap-fail tests still fail correctly.
- Update auth component description; mark B3 closed.
- Code review verdict PASS; static + fast suites green (231 / 13 skipped).

Batch report: _docs/03_implementation/batch_13_cycle3_report.md

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

tests/canvas_editor.test.tsx

@@ -184,7 +184,7 @@ describe('AZ-471 — CanvasEditor (draw / resize / multi-select / zoom / pan)',
     // an unhandled request triggers MSW's onUnhandledRequest:'error'. A 401
     // here keeps AuthProvider's `.catch` quiet (loading flips to false) and
     // satisfies AC-3 of AZ-456.
-    server.use(http.get('/api/admin/auth/refresh', () => new Response(null, { status: 401 })))
+    server.use(http.post('/api/admin/auth/refresh', () => new Response(null, { status: 401 })))
 
     // Force the container's clientWidth/Height (jsdom default = 0) so the
     // CanvasEditor's `useEffect(isVideo)` populates `imgSize` to 640×480.