Standardise frontend hook fetch error handling and mark Task 12 done

frontend/src/hooks/useJailDistribution.ts

@@ -7,6 +7,7 @@
 
 import { useCallback, useEffect, useRef, useState } from "react";
 import { fetchBansByJail } from "../api/dashboard";
+import { handleFetchError } from "../utils/fetchError";
 import type { BanOriginFilter, JailBanCount, TimeRange } from "../types/ban";
 
 // ---------------------------------------------------------------------------
@@ -65,9 +66,7 @@ export function useJailDistribution(
       })
       .catch((err: unknown) => {
         if (controller.signal.aborted) return;
-        setError(
-          err instanceof Error ? err.message : "Failed to fetch jail distribution",
-        );
+        handleFetchError(err, setError, "Failed to fetch jail distribution");
       })
       .finally(() => {
         if (!controller.signal.aborted) {