feat(panel): add sponsor slots fed from sponsors.sanaei.dev

Monthly sponsor placements need to change without cutting a panel
release. Panels now read 3X/sponsors.json from the MHSanaei/sponsors
repo (GitHub Pages on sponsors.sanaei.dev) and show active sponsors in
four slots: an overview banner, a rotating sidebar card (max three), the
login page and a new Sponsors page that also lists open placements.

An entry shows only while enable is not false and until is in the
future; links must be https and logos are png/webp/jpg by name only.
The list is cached for an hour and the last good copy survives upstream
failures; logos are proxied through /sponsors/logo/:name with failures
cached, so CSP stays 'self' and admin browsers never reach a third
party. Admins can hide a slot for 24h. Under XUI_DEBUG the panel reads
a sibling ../sponsors/3X checkout so edits can be previewed before push.

frontend/src/api/http-init.ts

@@ -196,6 +196,10 @@ export async function httpRequest(
   return { ok: true, status: res.status, statusText: res.statusText, data: parsed };
 }
 
+export function withBasePath(path: string): string {
+  return basePathPrefix + path;
+}
+
 export function setupHttp(): void {
   let basePath: string | null | undefined = window.X_UI_BASE_PATH;
   if (!basePath) {

frontend/src/api/queries/useSponsorsQuery.ts

@@ -0,0 +1,23 @@
+import { useQuery } from '@tanstack/react-query';
+
+import { HttpUtil } from '@/utils';
+import { keys } from '@/api/queryKeys';
+import type { SponsorList } from '@/generated/types';
+
+const EMPTY: SponsorList = { sponsors: [] };
+
+async function fetchSponsors(): Promise<SponsorList> {
+  const msg = await HttpUtil.get<SponsorList>('/sponsors', undefined, { silent: true });
+  if (!msg?.success || !msg.obj) return EMPTY;
+  return { contact: msg.obj.contact, sponsors: msg.obj.sponsors ?? [] };
+}
+
+export function useSponsorsQuery() {
+  const query = useQuery({
+    queryKey: keys.sponsors(),
+    queryFn: fetchSponsors,
+    staleTime: 60 * 60 * 1000,
+    retry: false,
+  });
+  return { data: query.data ?? EMPTY, fetched: query.isFetched };
+}

frontend/src/api/queryKeys.ts

@@ -1,4 +1,5 @@
 export const keys = {
+  sponsors: () => ['sponsors'] as const,
   server: {
     status: () => ['server', 'status'] as const,
     fail2banStatus: () => ['server', 'fail2banStatus'] as const,