fix(hooks): Forward abort signal to fetchBansByCountry in useDashboardCountryData

The useDashboardCountryData hook was creating an AbortController and checking
signal.aborted in callbacks, but was not passing the signal to the fetchBansByCountry
API call. This meant the HTTP request itself was never actually aborted.

Now the signal is forwarded, allowing proper request cancellation when the hook
unmounts or dependencies change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/hooks/useDashboardCountryData.ts

@@ -68,7 +68,7 @@ export function useDashboardCountryData(
     setLoading(true);
     setError(null);
 
-    fetchBansByCountry(timeRange, origin, source)
+    fetchBansByCountry(timeRange, origin, source, undefined, controller.signal)
       .then((data) => {
         if (controller.signal.aborted) return;
         setCountries(data.countries);