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/ConfigPanel.tsx

@@ -6,7 +6,7 @@ import { api, type ConfigItem, type PlexTestResult } from "../lib/api";
 import { notify } from "../lib/notifications";
 import Tooltip from "./Tooltip";
 import Tabs, { usePersistedTab } from "./Tabs";
-import { StateMessage } from "./QueryState";
+import { LoadingState, StateMessage } from "./QueryState";
 import { PageToolbar } from "./PageShell";
 import { Switch } from "./ui/form";
 import { DraftSaveBar, type SaveState } from "./ui/DraftSaveBar";
@@ -157,7 +157,7 @@ export default function ConfigPanel() {
     );
   }
   if (q.isLoading || !data) {
-    return <div className="p-4 max-w-3xl mx-auto text-muted">{t("config.loading")}</div>;
+    return <LoadingState label={t("config.loading")} />;
   }
 
   const groupKeys = Object.keys(data.groups).sort(