Fix join reminder notifications: status filter bug and daily 8 AM scheduling

[Copilot]

Two bugs caused join reminder notifications to show incorrect dates and be sent to the wrong recipients. Additionally, the reminder scheduling has been changed to a daily cadence.

Bugs fixed

• AdminStore.getInvitedPlayerIds — status filter silently dropped
  Kysely builders are immutable; the .where(statusFilter) result was never reassigned, so { statusFilter: 'pending' } was ignored and all invitations (including accepted/declined) were returned.

  // Before — filter discarded
  const builder = this.#db.selectFrom(...).select([...]);
  if (statusFilter) {
    builder.where('status', '=', statusFilter); // new builder thrown away
  }
  
  // After — filter applied
  let builder = this.#db.selectFrom(...).select([...]);
  if (statusFilter) {
    builder = builder.where('status', '=', statusFilter);
  }

• GameSession.#scheduleJoinRemindersTask — reminder rescheduled on every DO wake-up
  The reminder was scheduled as addHours(new Date(), 24). After the initial reminder fired (deleting the task from the scheduler), any subsequent DO hibernation/wake cycle with the game still pending would schedule another reminder 24h from that new wake time — producing repeated notifications with ever-increasing "N days ago" counts.

Scheduling change

Join reminders now fire at 8 AM every day (in the session's timezone) instead of once 24 hours after session creation. After each send, #sendJoinReminders reschedules itself for 8 AM the next day — mirroring the existing turn-reminder pattern. Rescheduling stops automatically when the game session is no longer pending or when there are no remaining pending invitees.

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[a-type]

Please change the game join reminder to be scheduled for 8 am every day, until the game session is no longer pending.

[Copilot]

Please change the game join reminder to be scheduled for 8 am every day, until the game session is no longer pending.

Done in 7228a10. Join reminders now fire at 8 AM every day in the session's timezone. After each send, #sendJoinReminders calls #scheduleJoinRemindersTask() to queue the next day's 8 AM alarm — matching the same pattern as turn reminders. Rescheduling stops automatically when the game is no longer pending (early-exit guard at the top of #sendJoinReminders) or when there are no remaining pending invitees.