fix: P0 post-deploy bug fixes from live testing

- EditHistoryModal: use raw fetch with /_matrix/client/v1/ path for
  relations API — Synapse only supports relations at v1, not v3 (fixes
  Sentry JAVASCRIPT-REACT-K / 404 error)
- RoomViewHeader: remove useReportRoomSupported spec-version gate —
  Synapse 1.114+ has the endpoint but only advertises spec v1.12;
  button now always shows for non-creator, non-server-notice rooms
- ReportRoomModal: handle M_UNRECOGNIZED/404 with "not supported by
  your homeserver" message
- RoomNavItem: add isServerNotice guard to Room Settings in sidebar
  context menu (was only guarded in header three-dots menu)
- initMatrix: bump setMaxListeners from 50 → 150 to prevent
  MaxListenersExceededWarning with large room lists
- RoomProfile: save topic with formatted_body + format when markdown
  syntax is detected; add markdown hint below topic textarea

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/ReportRoomModal.tsx

@@ -67,16 +67,19 @@ export function ReportRoomModal({ roomId, onClose }: ReportRoomModalProps) {
     submitReport(fullReason);
   };
 
-  const errcode =
+  const reportError =
     reportState.status === AsyncStatus.Error
-      ? (reportState.error as { errcode?: string })?.errcode
+      ? (reportState.error as { errcode?: string; httpStatus?: number })
       : undefined;
+  const errcode = reportError?.errcode;
   const errorMsg =
     errcode === 'M_LIMIT_EXCEEDED'
       ? 'You are being rate limited. Please wait before reporting again.'
       : errcode === 'M_FORBIDDEN'
         ? 'You cannot report this room.'
-        : 'Failed to submit report. Please try again.';
+        : errcode === 'M_UNRECOGNIZED' || reportError?.httpStatus === 404
+          ? 'Room reporting is not supported by your homeserver.'
+          : 'Failed to submit report. Please try again.';
 
   return (
     <Overlay open backdrop={<OverlayBackdrop />}>