Add WS reconnect logic + connection indicator in calendar

- useHotelSocket: reconnect with exponential backoff (up to 30s), return connected state, log errors to console
- BookingCalendar: show green/gray dot + Online/Offline label in toolbar
- CalendarPage: pass wsConnected prop

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/CalendarPage.tsx

@@ -49,7 +49,7 @@ export function CalendarPage() {
     }
   }, [])
 
-  const { send } = useHotelSocket({ slug, token: session?.token ?? null, onMessage: handleWsMessage })
+  const { send, connected } = useHotelSocket({ slug, token: session?.token ?? null, onMessage: handleWsMessage })
 
   const handleCreate = async (data: Partial<Booking>) => {
     try {
@@ -134,6 +134,7 @@ export function CalendarPage() {
           locks={locks}
           onDraftStart={handleDraftStart}
           onDraftCancel={handleDraftCancel}
+          wsConnected={connected}
         />
       </div>
     </div>