feat: Task 4 — paginated banned-IPs section on jail detail page

Backend:
- Add JailBannedIpsResponse Pydantic model (ban.py)
- Add get_jail_banned_ips() service: server-side pagination, optional
  IP substring search, geo enrichment on page slice only (jail_service.py)
- Add GET /api/jails/{name}/banned endpoint with page/page_size/search
  query params, 400/404/502 error handling (routers/jails.py)
- 23 new tests: 13 service tests + 10 router tests (all passing)

Frontend:
- Add JailBannedIpsResponse TS interface (types/jail.ts)
- Add jailBanned endpoint helper (api/endpoints.ts)
- Add fetchJailBannedIps() API function (api/jails.ts)
- Add BannedIpsSection component: Fluent UI DataGrid, debounced search
  (300 ms), prev/next pagination, page-size dropdown, per-row unban
  button, loading spinner, empty state, error MessageBar (BannedIpsSection.tsx)
- Mount BannedIpsSection in JailDetailPage between stats and patterns
- 12 new Vitest tests for BannedIpsSection (all passing)

frontend/src/api/endpoints.ts

@@ -38,6 +38,7 @@ export const ENDPOINTS = {
   // -------------------------------------------------------------------------
   jails: "/jails",
   jail: (name: string): string => `/jails/${encodeURIComponent(name)}`,
+  jailBanned: (name: string): string => `/jails/${encodeURIComponent(name)}/banned`,
   jailStart: (name: string): string => `/jails/${encodeURIComponent(name)}/start`,
   jailStop: (name: string): string => `/jails/${encodeURIComponent(name)}/stop`,
   jailIdle: (name: string): string => `/jails/${encodeURIComponent(name)}/idle`,

frontend/src/api/jails.ts

@@ -10,6 +10,7 @@ import { ENDPOINTS } from "./endpoints";
 import type {
   ActiveBanListResponse,
   IpLookupResponse,
+  JailBannedIpsResponse,
   JailCommandResponse,
   JailDetailResponse,
   JailListResponse,
@@ -224,3 +225,37 @@ export async function unbanAllBans(): Promise<UnbanAllResponse> {
 export async function lookupIp(ip: string): Promise<IpLookupResponse> {
   return get<IpLookupResponse>(ENDPOINTS.geoLookup(ip));
 }
+
+// ---------------------------------------------------------------------------
+// Jail-specific paginated bans
+// ---------------------------------------------------------------------------
+
+/**
+ * Fetch the currently banned IPs for a specific jail, paginated.
+ *
+ * Only the requested page is geo-enriched on the backend, so this call
+ * remains fast even when a jail has thousands of banned IPs.
+ *
+ * @param jailName - Jail name (e.g. `"sshd"`).
+ * @param page     - 1-based page number (default 1).
+ * @param pageSize - Items per page; max 100 (default 25).
+ * @param search   - Optional case-insensitive IP substring filter.
+ * @returns A {@link JailBannedIpsResponse} with paginated ban entries.
+ * @throws {ApiError} On non-2xx responses (404 if jail unknown, 502 if fail2ban down).
+ */
+export async function fetchJailBannedIps(
+  jailName: string,
+  page = 1,
+  pageSize = 25,
+  search?: string,
+): Promise<JailBannedIpsResponse> {
+  const params: Record<string, string> = {
+    page: String(page),
+    page_size: String(pageSize),
+  };
+  if (search !== undefined && search !== "") {
+    params.search = search;
+  }
+  const query = new URLSearchParams(params).toString();
+  return get<JailBannedIpsResponse>(`${ENDPOINTS.jailBanned(jailName)}?${query}`);
+}