feat(ui): shared LoadingState — a centered accent spinner instead of plain loading text

Replaces the plain "Loading…" text in every R3 loading branch with a single shared LoadingState
(a spinning lucide Loader2 in the accent colour + label, centered, role=status/aria-live) — one
component so all loads read the same and can be swapped for skeletons later in one place. Applied
across Feed, Channels, ChannelDiscovery, AuditLog, NotificationsPanel, Messages, Scheduler, Stats,
PlexBrowse (grid + subviews), PlexPlaylistView, ConfigPanel, DownloadCenter, AdminUsers, ChatThread.
Left the small "load more" footer and lazy Suspense fallbacks as-is.

frontend/src/components/Scheduler.tsx

@@ -18,7 +18,7 @@ import {
 } from "lucide-react";
 import { api, type SchedulerJob, type SchedulerStatus } from "../lib/api";
 import { useLiveQuery } from "../lib/useLiveQuery";
-import { StateMessage } from "./QueryState";
+import { LoadingState, StateMessage } from "./QueryState";
 import { useConfirm } from "./ConfirmProvider";
 import { relativeTime } from "../lib/format";
 import { notify } from "../lib/notifications";
@@ -429,7 +429,7 @@ export default function Scheduler() {
         {t("common.loadError")}
       </StateMessage>
     );
-  if (q.isLoading && !data) return <div className="p-8 text-muted">{t("scheduler.loading")}</div>;
+  if (q.isLoading && !data) return <LoadingState label={t("scheduler.loading")} />;
   if (!data) return <div className="p-8 text-muted">{t("common.somethingWrong")}</div>;
 
   const quotaPct = data.quota.daily_budget