Fix connection accept: stale cache, hidden button, and false 409 error

- incomingQuery: staleTime:0 + refetchOnMount:'always' so pending
  requests are always fresh when components mount (was inheriting
  5-min global staleTime, causing empty pendingRequestIds on nav)
- NotificationsPage: show Accept button while incoming data loads
  (was hidden during async gap); disable with spinner until ready
- Both toast and page: treat 409 as success ("already accepted")
  instead of showing error (fixes race when both fire respond)

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

frontend/src/components/notifications/NotificationToaster.tsx

@@ -36,9 +36,15 @@ export default function NotificationToaster() {
         await respondRef.current({ requestId, action });
         toast.dismiss(loadingId);
         toast.success(action === 'accept' ? 'Connection accepted' : 'Request declined');
-      } catch (err) {
+      } catch (err: any) {
         toast.dismiss(loadingId);
-        toast.error(getErrorMessage(err, 'Failed to respond to request'));
+        // 409 means the request was already resolved (e.g. accepted via notification center)
+        const status = err?.response?.status;
+        if (status === 409) {
+          toast.success(action === 'accept' ? 'Connection already accepted' : 'Request already resolved');
+        } else {
+          toast.error(getErrorMessage(err, 'Failed to respond to request'));
+        }
       } finally {
         respondingRef.current.delete(requestId);
       }

frontend/src/components/notifications/NotificationsPage.tsx

@@ -31,7 +31,7 @@ export default function NotificationsPage() {
     deleteNotification,
   } = useNotifications();
 
-  const { incomingRequests, respond, isResponding } = useConnections();
+  const { incomingRequests, respond, isResponding, isLoadingIncoming } = useConnections();
   const queryClient = useQueryClient();
   const navigate = useNavigate();
   const [filter, setFilter] = useState<Filter>('all');
@@ -93,7 +93,13 @@ export default function NotificationsPage() {
       }
       toast.success(action === 'accept' ? 'Connection accepted' : 'Request declined');
     } catch (err) {
-      toast.error(getErrorMessage(err, 'Failed to respond'));
+      // 409 means the request was already resolved (e.g. accepted via toast)
+      const status = (err as any)?.response?.status;
+      if (status === 409) {
+        toast.success(action === 'accept' ? 'Connection already accepted' : 'Request already resolved');
+      } else {
+        toast.error(getErrorMessage(err, 'Failed to respond'));
+      }
     }
   };
 
@@ -218,22 +224,23 @@ export default function NotificationsPage() {
                   {/* Connection request actions (inline) */}
                   {notification.type === 'connection_request' &&
                     notification.source_id &&
-                    pendingRequestIds.has(notification.source_id) && (
+                    !notification.is_read &&
+                    (isLoadingIncoming || pendingRequestIds.has(notification.source_id)) && (
                       <div className="flex items-center gap-1.5 shrink-0">
                         <Button
                           size="sm"
                           onClick={(e) => { e.stopPropagation(); handleConnectionRespond(notification, 'accept'); }}
-                          disabled={isResponding}
+                          disabled={isResponding || isLoadingIncoming}
                           className="gap-1 h-7 text-xs"
                         >
-                          {isResponding ? <Loader2 className="h-3 w-3 animate-spin" /> : <Check className="h-3 w-3" />}
+                          {(isResponding || isLoadingIncoming) ? <Loader2 className="h-3 w-3 animate-spin" /> : <Check className="h-3 w-3" />}
                           Accept
                         </Button>
                         <Button
                           variant="ghost"
                           size="sm"
                           onClick={(e) => { e.stopPropagation(); handleConnectionRespond(notification, 'reject'); }}
-                          disabled={isResponding}
+                          disabled={isResponding || isLoadingIncoming}
                           className="h-7 text-xs"
                         >
                           <X className="h-3 w-3" />

frontend/src/hooks/useConnections.ts

@@ -20,6 +20,8 @@ export function useConnections() {
       const { data } = await api.get<ConnectionRequest[]>('/connections/requests/incoming');
       return data;
     },
+    staleTime: 0,
+    refetchOnMount: 'always',
   });
 
   const outgoingQuery = useQuery({
@@ -95,6 +97,7 @@ export function useConnections() {
     incomingRequests: incomingQuery.data ?? [],
     outgoingRequests: outgoingQuery.data ?? [],
     isLoading: connectionsQuery.isLoading,
+    isLoadingIncoming: incomingQuery.isLoading,
     search: searchMutation.mutateAsync,
     isSearching: searchMutation.isPending,
     sendRequest: sendRequestMutation.mutateAsync,