feat: task 1.8 logout flow + cross-tab sync + strict tsconfig

- src/auth/logout.ts: performLogout({ queryClient, navigate? })
  orchestration. Calls store.logout(), clears query cache, navigates
  to /login. Server-call failures swallowed; local state still flips
  to anonymous.
- src/auth/cross-tab-sync.ts: startCrossTabSync(). Subscribes to the
  auth store and bumps trm-auth-version in localStorage on status
  transitions; listens for storage events and re-runs initialize()
  when another tab bumps. Idempotent via module-level guard. No-ops
  if localStorage is unavailable.
- src/ui/components/logout-button.tsx: <LogoutButton> wraps shadcn
  Button. Pass-through props but locks onClick / disabled / children.
  Local isLoggingOut for "Signing out..." indicator + double-click
  guard.
- src/auth/bootstrap.tsx: <AuthBootstrap> now calls startCrossTabSync()
  alongside the existing init steps. Single mount point.
- src/auth/index.ts: re-export performLogout + startCrossTabSync.
- src/routes/_authed/index.tsx: replaced the inline sign-out button
  with <LogoutButton />. The existing useEffect on 'anonymous' status
  handles navigation when cross-tab sync fires.

Bonus: tsconfig.app.json now has "strict": true. TanStack Router emits
a conditional-type error ("strictNullChecks must be enabled") in
editors when strict is off; tsc -b was lenient. Caught in 1.7's
review. Typecheck remained green after enabling.

.planning/ROADMAP.md

@@ -56,7 +56,7 @@ These rules govern every task. Any deviation must be discussed and documented as
 | 1.5  | [Directus auth client (cookie mode + refresh)](./phase-1-foundation/05-directus-auth-client.md)              | 🟩     | `38fe2e3` |
 | 1.6  | [Login page](./phase-1-foundation/06-login-page.md)                                                          | 🟩     | `7215cb5` |
 | 1.7  | [Routing skeleton (TanStack Router + role-aware guards)](./phase-1-foundation/07-routing-skeleton.md)        | 🟩     | `f4a5e5b` |
-| 1.8  | [Logout flow](./phase-1-foundation/08-logout-flow.md)                                                        | ⬜     | —         |
+| 1.8  | [Logout flow](./phase-1-foundation/08-logout-flow.md)                                                        | 🟩     | `PENDING_SHA` |
 | 1.9  | [Gitea CI + Dockerfile + nginx static serve](./phase-1-foundation/09-gitea-ci-and-dockerfile.md)             | ⬜     | —         |
 | 1.10 | [Compose service block in trm/deploy](./phase-1-foundation/10-deploy-compose-block.md)                       | ⬜     | —         |