feat(files): API tokens in Settings, the Hub folder in Files, a notice before a token runs out

Settings gains an API tokens tab: a row per token (name and prefix; each
folder with its rights; last use and expiry, "expires soon" marked),
revoked from its menu behind a confirm. A new token is the Hub exchange in
one click, or folders and rights picked per folder (no Write where an
upload cannot land); expiry 30/90 days, 1 year or never (warned). The
token shows once in the same dialog, with Copy and a ready curl line.

The Hub folder closes the Sources in the Files rail, takes uploads and
moved-in files. A token about to run out warns its user once, a week
before (the Files GC's sixth pass); the notice opens the tokens tab.

frontend/src/lib/api/files.ts

@@ -3,8 +3,9 @@
 import { getActiveAccount, req, uploadReq } from "./core";
 import type { DownloadJob } from "./downloads";
 
-// "source": filled by where a file came from (YouTube, Plex, a site, uploads); "own": made by the user.
-export type FolderKind = "source" | "own";
+// "source": filled by where a file came from (YouTube, Plex, a site, uploads); "own": made by the user;
+// "hub": the one folder the user swaps files with their hub machine through (made by its token).
+export type FolderKind = "source" | "own" | "hub";
 
 export interface FileFolder {
   id: number;