fix(schedulers): wire recurring-task spawn + deliver event reminders

Drift-audit Group 2 (Phase-8 amputation — live wiring, no consumer):

- Recurring tasks never recurred: spawn_recurring_tasks() had no caller.
  Register it as a 15-min interval job in the event scheduler (which
  app.py already starts/stops). Also add a deleted_at IS NULL guard to
  the spawn query in the same change, so a trashed recurring parent can
  never resurrect children once the sweep is live.
- Event reminders were stamped reminder_sent_at but never delivered.
  _fire_reminders now creates an 'event_reminder' in-app notification
  before stamping, so a delivery failure stays retryable. Frontend
  NotificationsPanel renders the new type (⏰ + message); message logic
  pulled into a notifMessage() helper.
- Remove the dead _fire_push_notif no-op stub (push left in Phase 8) and
  its three create_task call sites — no more throwaway tasks per share.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/fabledassistant/services/recurrence.py

@@ -115,6 +115,9 @@ async def spawn_recurring_tasks() -> int:
                 and_(
                     Note.recurrence_rule.isnot(None),
                     Note.recurrence_next_spawn_at <= now,
+                    # Never spawn children off a trashed parent — that would
+                    # resurrect work the user explicitly deleted.
+                    Note.deleted_at.is_(None),
                 )
             )
         )