Stage 11: polish, cross-cutting concerns & hardening

- 11.1 MainLayout health indicator: warning MessageBar when fail2ban offline
- 11.2 formatDate utility + TimezoneProvider + GET /api/setup/timezone
- 11.3 Responsive sidebar: auto-collapse <640px, media query listener
- 11.4 PageFeedback (PageLoading/PageError/PageEmpty), BanTable updated
- 11.5 prefers-reduced-motion: disable sidebar transition
- 11.6 WorldMap ARIA: role/tabIndex/aria-label/onKeyDown for countries
- 11.7 Health transition logging (fail2ban_came_online/went_offline)
- 11.8 Global handlers: Fail2BanConnectionError/ProtocolError -> 502
- 11.9 379 tests pass, 82% coverage, ruff+mypy+tsc+eslint clean
- Timezone endpoint: setup_service.get_timezone, 5 new tests

frontend/src/api/setup.ts

@@ -10,6 +10,7 @@ import type {
   SetupRequest,
   SetupResponse,
   SetupStatusResponse,
+  SetupTimezoneResponse,
 } from "../types/setup";
 
 /**
@@ -30,3 +31,15 @@ export async function getSetupStatus(): Promise<SetupStatusResponse> {
 export async function submitSetup(data: SetupRequest): Promise<SetupResponse> {
   return api.post<SetupResponse>(ENDPOINTS.setup, data);
 }
+
+/**
+ * Fetch the IANA timezone configured during setup.
+ *
+ * Used by the frontend to convert UTC timestamps to the local timezone
+ * chosen by the administrator.
+ *
+ * @returns The configured timezone identifier (e.g. `"Europe/Berlin"`).
+ */
+export async function fetchTimezone(): Promise<SetupTimezoneResponse> {
+  return api.get<SetupTimezoneResponse>(ENDPOINTS.setupTimezone);
+}