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/components/WorldMap.tsx

@@ -102,9 +102,23 @@ function GeoLayer({
             <g
               key={geo.rsmKey}
               style={{ cursor: cc ? "pointer" : "default" }}
+              role={cc ? "button" : undefined}
+              tabIndex={cc ? 0 : undefined}
+              aria-label={cc
+                ? `${cc}: ${String(count)} ban${count !== 1 ? "s" : ""}${
+                    isSelected ? " (selected)" : ""
+                  }`
+                : undefined}
+              aria-pressed={isSelected || undefined}
               onClick={(): void => {
                 if (cc) handleClick(cc);
               }}
+              onKeyDown={(e): void => {
+                if (cc && (e.key === "Enter" || e.key === " ")) {
+                  e.preventDefault();
+                  handleClick(cc);
+                }
+              }}
             >
               <Geography
                 geography={geo}
@@ -170,7 +184,11 @@ export function WorldMap({
   const maxCount = Math.max(0, ...Object.values(countries));
 
   return (
-    <div className={styles.mapWrapper}>
+    <div
+      className={styles.mapWrapper}
+      role="img"
+      aria-label="World map showing banned IP counts by country. Click a country to filter the table below."
+    >
       <ComposableMap
         projection="geoMercator"
         projectionConfig={{ scale: 130, center: [10, 20] }}