fix(calls): the call bar shows "Call disconnected" and reconnects when sync is back (#318)

After a homeserver stall Element Call showed "Connection lost" while the
call bar still looked joined. Handle the fork's io.lotus.call_error:
show "Call disconnected" with a Reconnect button (io.lotus.reconnect),
and reconnect automatically once sync is back.

Fixes #318

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/plugins/call/callError.ts

@@ -0,0 +1,14 @@
+/**
+ * [Gitea #318] The fork's `io.lotus.call_error`: its error page is showing
+ * (`{ code, recoverable }`) or was cleared (`{ code: null }`).
+ */
+export type CallErrorState = { code: string; recoverable: boolean } | null;
+
+/** Pure: parse a report; undefined for garbage (ignored). */
+export function parseCallError(data: unknown): CallErrorState | undefined {
+  if (typeof data !== 'object' || data === null) return undefined;
+  const { code, recoverable } = data as { code?: unknown; recoverable?: unknown };
+  if (code === null) return null;
+  if (typeof code !== 'string' || !code) return undefined;
+  return { code, recoverable: recoverable === true };
+}