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/AdminUsers.tsx

@@ -7,7 +7,7 @@ import { notify } from "../lib/notifications";
 import { ADMIN_USERS_TAB_KEY } from "../lib/adminUsersTab";
 import Tooltip from "./Tooltip";
 import { Section } from "./ui/form";
-import { StateMessage } from "./QueryState";
+import { LoadingState, StateMessage } from "./QueryState";
 import { useConfirm } from "./ConfirmProvider";
 import Tabs, { usePersistedTab } from "./Tabs";
 import { PageToolbar } from "./PageShell";
@@ -165,7 +165,7 @@ function UsersRoles({ me }: { me: Me }) {
           {t("common.loadError")}
         </StateMessage>
       ) : q.isLoading && !q.data ? (
-        <p className="text-sm text-muted">{t("common.loading")}</p>
+        <LoadingState />
       ) : rows.length === 0 ? (
         <p className="text-sm text-muted">{t("users.roles.empty")}</p>
       ) : (
@@ -319,7 +319,7 @@ function AdminInvites() {
           {t("common.loadError")}
         </StateMessage>
       ) : invites.isLoading && !invites.data ? (
-        <p className="text-sm text-muted">{t("common.loading")}</p>
+        <LoadingState />
       ) : pending.length === 0 ? (
         <p className="text-sm text-muted">{t("settings.invites.noPending")}</p>
       ) : (