Stage 9: ban history — backend service, router, frontend history page

- history.py models: HistoryBanItem, HistoryListResponse, IpTimelineEvent, IpDetailResponse
- history_service.py: list_history() with dynamic WHERE clauses (range/jail/ip
  prefix/all-time), get_ip_detail() with timeline aggregation
- history.py router: GET /api/history + GET /api/history/{ip} (404 for unknown)
- Fixed latent bug in ban_service._parse_data_json: json.loads('null') -> None
  -> AttributeError; now checks isinstance(parsed, dict) before assigning obj
- 317 tests pass (27 new), ruff + mypy clean (46 files)
- types/history.ts, api/history.ts, hooks/useHistory.ts created
- HistoryPage.tsx: filter bar (time range/jail/IP), DataGrid table,
  high-ban-count row highlighting, per-IP IpDetailView with timeline,
  pagination
- Frontend tsc + ESLint clean (0 errors/warnings)
- Tasks.md Stage 9 marked done

frontend/src/api/history.ts

@@ -0,0 +1,53 @@
+/**
+ * API functions for the ban history endpoints.
+ */
+
+import { get } from "./client";
+import { ENDPOINTS } from "./endpoints";
+import type {
+  HistoryListResponse,
+  HistoryQuery,
+  IpDetailResponse,
+} from "../types/history";
+
+/**
+ * Fetch a paginated list of historical bans with optional filters.
+ */
+export async function fetchHistory(
+  query: HistoryQuery = {},
+): Promise<HistoryListResponse> {
+  const params = new URLSearchParams();
+  if (query.range) params.set("range", query.range);
+  if (query.jail) params.set("jail", query.jail);
+  if (query.ip) params.set("ip", query.ip);
+  if (query.page !== undefined) params.set("page", String(query.page));
+  if (query.page_size !== undefined)
+    params.set("page_size", String(query.page_size));
+
+  const qs = params.toString();
+  const url = qs
+    ? `${ENDPOINTS.history}?${qs}`
+    : ENDPOINTS.history;
+  return get<HistoryListResponse>(url);
+}
+
+/**
+ * Fetch the full ban history for a single IP address.
+ *
+ * @returns null when the server returns 404 (no history for this IP).
+ */
+export async function fetchIpHistory(ip: string): Promise<IpDetailResponse | null> {
+  try {
+    return await get<IpDetailResponse>(ENDPOINTS.historyIp(ip));
+  } catch (err: unknown) {
+    if (
+      typeof err === "object" &&
+      err !== null &&
+      "status" in err &&
+      (err as { status: number }).status === 404
+    ) {
+      return null;
+    }
+    throw err;
+  }
+}