[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/tile_split_zoom.test.tsx

@@ -117,7 +117,7 @@ function datasetRowFromAnnotation(a: AnnotationListItem): DatasetItem {
 beforeEach(() => {
   seedBearer()
   server.use(
-    http.get('/api/admin/auth/refresh', () => new Response(null, { status: 401 })),
+    http.post('/api/admin/auth/refresh', () => new Response(null, { status: 401 })),
     // FlightProvider mounts a user-settings fetch when authenticated. The
     // dataset surface does not depend on it; we satisfy MSW's unhandled-
     // request gate with a 404 so the noise does not pollute the report.