fix(search-autocomplete): address PR #542 review issues

- Fix race condition: AbortController cancels in-flight autocomplete
  requests on each keystroke; stale responses no longer overwrite fresh ones
- Remove acTrigger state hack; onFocus calls fetchSuggestions directly
- Cap autocomplete input at 200 chars server-side (400 on violation)
- Filter Nominatim suggestions with empty osm_id segments
- Revert getPlaceDetails OSM branch from unconditional parallel fetch to
  conditional serial: Nominatim called only when Overpass lacks coords/address
- Wire places.loadingDetails i18n key to Loader2 spinner via aria-label/role
- Add tests: MAPS-017, MAPS-040c, MAPS-093, FE-MAPS-004

server/src/routes/maps.ts

@@ -39,6 +39,10 @@ router.post('/autocomplete', authenticate, async (req: Request, res: Response) =
     return res.status(400).json({ error: 'Input is required' });
   }
 
+  if (input.length > 200) {
+    return res.status(400).json({ error: 'Input too long (max 200 chars)' });
+  }
+
   if (locationBias) {
     const { low, high } = locationBias;
     if (!low || !high