feat(calls): EC iframe load watchdog + recovery UI; avatar decorations on call tiles

- CallEmbed: 25s load watchdog that fails fast on iframe error / preparing-error /
  timeout instead of hanging on a permanent spinner; additive onLoadError API,
  cleared on ready/capabilities/joined.
- CallView: user-visible "call failed to load" overlay with Retry/Leave (folds +
  tokens) via a new useCallLoadError hook.
- CallMemberCard: wrap the participant avatar in AvatarDecoration so decorations
  render in the call roster (the tile rendered UserAvatar bare while member lists
  already wrapped it).

Addresses LOTUS_BUGS item 3 (avatar decorations in calls) and EC iframe failure monitoring.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/hooks/useCallEmbed.ts

@@ -3,6 +3,7 @@ import { MatrixClient, Room } from 'matrix-js-sdk';
 import { useSetAtom } from 'jotai';
 import {
   CallEmbed,
+  CallLoadErrorReason,
   ElementCallThemeKind,
   ElementWidgetActions,
   useClientWidgetApiEvent,
@@ -156,6 +157,26 @@ export const useCallJoined = (embed?: CallEmbed): boolean => {
   return joined;
 };
 
+/**
+ * Surfaces a load failure (watchdog timeout or iframe error) from the embedded
+ * Element Call iframe so the UI can show a recovery affordance instead of an
+ * indefinite "Loading..." spinner.
+ */
+export const useCallLoadError = (embed?: CallEmbed): CallLoadErrorReason | undefined => {
+  const [error, setError] = useState<CallLoadErrorReason | undefined>(() => embed?.loadFailed);
+
+  useEffect(() => {
+    if (!embed) {
+      setError(undefined);
+      return undefined;
+    }
+    setError(embed.loadFailed);
+    return embed.onLoadError((reason) => setError(reason));
+  }, [embed]);
+
+  return error;
+};
+
 export const useCallHangupEvent = (embed: CallEmbed, callback: () => void) => {
   useClientWidgetApiEvent(embed.call, ElementWidgetActions.HangupCall, callback);
   useClientWidgetApiEvent(embed.call, ElementWidgetActions.Close, callback);