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/Stats.tsx

@@ -7,7 +7,7 @@ import { formatEta, quotaActionLabel } from "../lib/format";
 import { notify } from "../lib/notifications";
 import { LS, useAccountPersistedState } from "../lib/storage";
 import Tooltip from "./Tooltip";
-import { StateMessage } from "./QueryState";
+import { LoadingState, StateMessage } from "./QueryState";
 import { Section, SettingRow } from "./ui/form";
 import { useMe } from "../lib/useMe";
 
@@ -120,7 +120,7 @@ function Overview({ me }: { me: Me }) {
             {t("common.loadError")}
           </StateMessage>
         ) : (
-          <div className="text-muted text-sm">{t("stats.sync.loading")}</div>
+          <LoadingState label={t("stats.sync.loading")} />
         )}
       </Section>
 
@@ -252,7 +252,7 @@ function SystemStats() {
           {t("common.loadError")}
         </StateMessage>
       ) : q.isLoading ? (
-        <div className="text-muted py-8">{t("stats.loading")}</div>
+        <LoadingState label={t("stats.loading")} />
       ) : !data ? (
         <div className="text-muted py-8">{t("stats.noData")}</div>
       ) : (