feat(reminders): per-occurrence reminders for recurring events

Drift-audit Group 8 (final item). _fire_reminders previously gated on the
base row (reminder_sent_at IS NULL AND start_dt > now), so a recurring event
reminded at most once ever — once the first occurrence passed, no future
occurrence qualified.

Now recurring events are evaluated every sweep against their next occurrence
(rrulestr.after(now)), and reminder_sent_at stores the start of the occurrence
last reminded about. Each new occurrence has a distinct marker, so it re-arms
and fires exactly once per occurrence. One-shot events keep the classic
NULL gate. Also adds the deleted_at filter so trashed events stop reminding.

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

src/fabledassistant/services/event_scheduler.py

@@ -16,7 +16,8 @@ from datetime import datetime, timedelta, timezone
 
 from apscheduler.schedulers.background import BackgroundScheduler
 from apscheduler.triggers.interval import IntervalTrigger
-from sqlalchemy import select
+from dateutil.rrule import rrulestr
+from sqlalchemy import and_, or_, select
 
 from fabledassistant.models import async_session
 from fabledassistant.models.event import Event
@@ -32,7 +33,13 @@ _loop: asyncio.AbstractEventLoop | None = None
 # ---------------------------------------------------------------------------
 
 async def _fire_reminders() -> None:
-    """Find events with reminders due in the next 5 minutes and fire push notifications."""
+    """Fire in-app reminders for events whose reminder time has arrived.
+
+    One-shot events fire once (gated on reminder_sent_at IS NULL). Recurring
+    events fire once PER OCCURRENCE: reminder_sent_at stores the start of the
+    occurrence we last reminded about, so each new occurrence re-arms the
+    reminder instead of the whole series firing only once.
+    """
     now = datetime.now(timezone.utc)
     window_end = now + timedelta(minutes=5)
 
@@ -40,19 +47,38 @@ async def _fire_reminders() -> None:
         result = await session.execute(
             select(Event).where(
                 Event.reminder_minutes.isnot(None),
-                Event.reminder_sent_at.is_(None),
-                Event.start_dt > now,  # event hasn't started yet
-                # reminder fires when now >= start_dt - reminder_minutes
-                # i.e. start_dt <= now + reminder_minutes (approximated by window_end check)
+                Event.deleted_at.is_(None),
+                or_(
+                    # Recurring events are evaluated every sweep against their
+                    # next occurrence (the base start_dt is long past).
+                    Event.recurrence.isnot(None),
+                    # One-shot events: classic gate.
+                    and_(Event.reminder_sent_at.is_(None), Event.start_dt > now),
+                ),
             )
         )
         candidates = list(result.scalars().all())
 
-    to_notify: list[Event] = []
+    # (event_id, occurrence_start) — occurrence_start is also the dedup marker
+    # written to reminder_sent_at, so a given occurrence reminds exactly once.
+    to_notify: list[tuple[int, datetime]] = []
     for event in candidates:
-        reminder_dt = event.start_dt - timedelta(minutes=event.reminder_minutes)
-        if reminder_dt <= window_end:
-            to_notify.append(event)
+        if event.recurrence:
+            try:
+                rule = rrulestr(event.recurrence, dtstart=event.start_dt, ignoretz=False)
+                occ = rule.after(now, inc=True)
+            except Exception:
+                logger.warning("Failed to expand RRULE for event %d reminder", event.id, exc_info=True)
+                continue
+            if occ is None:
+                continue
+            reminder_dt = occ - timedelta(minutes=event.reminder_minutes)
+            if reminder_dt <= window_end and event.reminder_sent_at != occ:
+                to_notify.append((event.id, occ))
+        else:
+            reminder_dt = event.start_dt - timedelta(minutes=event.reminder_minutes)
+            if reminder_dt <= window_end:
+                to_notify.append((event.id, event.start_dt))
 
     if not to_notify:
         return
@@ -61,22 +87,23 @@ async def _fire_reminders() -> None:
     from fabledassistant.services.notifications import create_in_app_notification
 
     async with async_session() as session:
-        for event in to_notify:
-            result = await session.execute(
-                select(Event).where(Event.id == event.id)
-            )
-            ev = result.scalar_one_or_none()
-            if ev is None or ev.reminder_sent_at is not None:
+        for event_id, occurrence_start in to_notify:
+            ev = (await session.execute(
+                select(Event).where(Event.id == event_id)
+            )).scalar_one_or_none()
+            # Skip if this exact occurrence was already reminded (covers a
+            # concurrent sweep and the one-shot already-sent case).
+            if ev is None or ev.reminder_sent_at == occurrence_start:
                 continue
             await create_in_app_notification(ev.user_id, "event_reminder", {
                 "event_id": ev.id,
                 "title": ev.title,
-                "start_dt": ev.start_dt.isoformat() if ev.start_dt else None,
+                "start_dt": occurrence_start.isoformat(),
                 "url": "/calendar",
             })
-            # Stamp only after the notification is created, so a delivery
-            # failure leaves the reminder eligible to retry next sweep.
-            ev.reminder_sent_at = datetime.now(timezone.utc)
+            # Stamp the occurrence marker only after the notification is
+            # created, so a delivery failure leaves it eligible to retry.
+            ev.reminder_sent_at = occurrence_start
         await session.commit()