Refactor shared data source selection for dashboard and map

frontend/src/utils/queryUtils.ts

@@ -3,6 +3,7 @@
  */
 
 import type { HistoryQuery } from "../types/history";
+import type { TimeRange } from "../types/ban";
 
 /**
  * Compare two history query objects for semantic equality.
@@ -25,3 +26,13 @@ export function areHistoryQueriesEqual(
     a.page_size === b.page_size
   );
 }
+
+/**
+ * Return the data source for the given dashboard time range.
+ *
+ * @param range - The selected time range.
+ * @returns The backend source to query.
+ */
+export function getDataSource(range: TimeRange): "fail2ban" | "archive" {
+  return range === "24h" ? "fail2ban" : "archive";
+}