refactor(scribe): retire calendar/events + person/place/list entities (backend)

Narrow Scribe to a Claude-Code work system-of-record (milestone #194,
decision note #1759). Wholesale removal per rule #22 — backend + schema half.

Calendar/events + CalDAV: delete models/event, services/{events,caldav,
caldav_sync}, routes/events, mcp/tools/events; strip event branches from
backup (bump v3->v4), dashboard (upcoming_events), trash, recent, and the
mcp server read-only allowlist + instructions.

Typed entities (person/place/list): delete mcp/tools/entities; drop the
notes.metadata (entity_meta) column from model/service/routes and the
knowledge browse service. note_type STAYS — it also marks 'process' notes.

Scheduler: event_scheduler -> recurrence_scheduler, keeping only the
recurring-task spawn job (drops event reminders + CalDAV sync).

Schema: migration 0069 drops the events table + notes.metadata column +
orphan caldav settings rows (faithful downgrade recreates them).

KEEP: recurrence.py (task recurrence), notifications task reminders, graph
view, and every work surface. Frontend + plugin/docs true-up follow next.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BPtbSzA4JLMAKgFZ8VTg7Q

src/scribe/services/recurrence_scheduler.py

@@ -0,0 +1,64 @@
+"""Scheduler for recurring-task spawning.
+
+Every 15 minutes, creates the next occurrence of any recurring task whose spawn
+time has arrived — draining `recurrence_next_spawn_at`, which is armed on task
+completion. Without this job, recurring tasks would never recur.
+
+Uses the BackgroundScheduler pattern shared with the other *_scheduler modules.
+(Formerly event_scheduler.py, which also ran event reminders + CalDAV sync;
+those were removed when the calendar surface was retired.)
+"""
+from __future__ import annotations
+
+import asyncio
+import logging
+
+from apscheduler.schedulers.background import BackgroundScheduler
+from apscheduler.triggers.interval import IntervalTrigger
+
+logger = logging.getLogger(__name__)
+
+_scheduler: BackgroundScheduler | None = None
+_loop: asyncio.AbstractEventLoop | None = None
+
+
+async def _run_recurrence_spawn() -> None:
+    from scribe.services.recurrence import spawn_recurring_tasks  # noqa: PLC0415
+    try:
+        await spawn_recurring_tasks()
+    except Exception:
+        logger.warning("Recurring-task spawn job failed", exc_info=True)
+
+
+def _run_recurrence_spawn_threadsafe(loop: asyncio.AbstractEventLoop) -> None:
+    asyncio.run_coroutine_threadsafe(_run_recurrence_spawn(), loop)
+
+
+def start_recurrence_scheduler(loop: asyncio.AbstractEventLoop) -> None:
+    global _scheduler, _loop
+    if _scheduler is not None:
+        return
+    _loop = loop
+    _scheduler = BackgroundScheduler()
+
+    # Spawn the next occurrence of due recurring tasks every 15 minutes.
+    # Without this job, recurrence_next_spawn_at is armed on completion but
+    # never drained, so recurring tasks never recur.
+    _scheduler.add_job(
+        _run_recurrence_spawn_threadsafe,
+        trigger=IntervalTrigger(minutes=15),
+        args=[loop],
+        id="recurrence_spawn",
+        replace_existing=True,
+    )
+
+    _scheduler.start()
+    logger.info("Recurrence scheduler started (recurring-task spawn every 15m)")
+
+
+def stop_recurrence_scheduler() -> None:
+    global _scheduler
+    if _scheduler is not None:
+        _scheduler.shutdown(wait=False)
+        _scheduler = None
+        logger.info("Recurrence scheduler stopped")