Scheduled meetings: deliver a background push (fixes no iOS notification)

Root cause: the scheduled-meeting INVITE (routes.js) and the ~10-min REMINDER
(reminders.js) both notified only via CHAT.pushToUser — the WebSocket channel,
which only reaches an OPEN tab with a live socket. Neither called
PUSH.sendToUser, the path that produces a background APNs/FCM/web-push alert.
On iOS the webview is suspended in the background, so the WS event was simply
missed and no notification appeared. (Chat messages already call PUSH.sendToUser,
which is why chat notices arrive on iOS but meeting ones didn't.)

Fix:
- schedule invite: also PUSH.sendToUser to every invited participant + group
  members (kind:'meeting', id:roomCode) so a closed app is notified.
- reminders.js: also PUSH.sendToUser to all reminder recipients.
- client: a kind:'meeting' notification tap now opens the Meeting tab + its list
  (both the live-tab open-chat handler and the cold-boot openKind path), instead
  of calling selectChat with an unsupported kind.

Also: APPSTORE_SUBMISSION.md §8 updated — the UGC Report/Block gate (guideline
1.2) is now implemented, with a suggested reviewer note.

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

server/reminders.js

@@ -2,6 +2,7 @@
 // group members, and invited participants. Runs on a 60s tick; marks each meeting reminded.
 const R = require('./repos');
 const CHAT = require('./chat');
+const PUSH = require('./push'); // native/web background push so a CLOSED app still gets the reminder
 
 async function tick() {
   try {
@@ -13,7 +14,8 @@ async function tick() {
       invited.forEach((id) => recipients.add(id));
       if (s.group_id) { try { (await R.conversations.members(s.group_id)).forEach((m) => recipients.add(m)); } catch (_) {} }
       const evt = { type: 'meeting-reminder', meeting: { id: s.id, title: s.title, scheduledAt: s.scheduled_at, room: s.room_code } };
-      recipients.forEach((uid) => { try { CHAT.pushToUser(uid, evt); } catch (_) {} });
+      recipients.forEach((uid) => { try { CHAT.pushToUser(uid, evt); } catch (_) {} });                 // open tab
+      recipients.forEach((uid) => { try { PUSH.sendToUser(uid, { title: 'Meeting starting soon', body: (s.title || 'Your meeting') + ' starts in ~10 minutes', kind: 'meeting', id: s.room_code, tag: 'meet:' + s.room_code }); } catch (_) {} }); // closed app (iOS APNs etc.)
       await R.scheduledMeetings.markReminded(s.id);
     }
   } catch (_) { /* never let the timer die */ }