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/types/jail.ts

@@ -198,6 +198,26 @@ export interface UnbanAllResponse {
   count: number;
 }
 
+// ---------------------------------------------------------------------------
+// Jail-specific paginated bans
+// ---------------------------------------------------------------------------
+
+/**
+ * Paginated response from `GET /api/jails/{name}/banned`.
+ *
+ * Mirrors `JailBannedIpsResponse` from `backend/app/models/ban.py`.
+ */
+export interface JailBannedIpsResponse {
+  /** Active ban entries for the current page. */
+  items: ActiveBan[];
+  /** Total matching entries (after applying any search filter). */
+  total: number;
+  /** Current page number (1-based). */
+  page: number;
+  /** Number of items per page. */
+  page_size: number;
+}
+
 export interface GeoDetail {
   /** ISO 3166-1 alpha-2 country code (e.g. `"DE"`), or `null`. */
   country_code: string | null;