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/mcp/server.py

@@ -45,15 +45,10 @@ What each part is for, and when to reach for it:
   record (note, task, issue) with it via system_ids so research, build-work, and
   fixes for the same area line up, and recurring problem-spots surface. Manage
   with create_system / list_systems / get_system.
-- Typed entities (person/place/list): structured records about people, places,
-  and checklists.
 
 Mechanics:
 - Notes and Tasks share a model; tasks are notes with is_task=True.
 - Use the *_note tools for notes, the *_task tools for tasks. Don't mix them.
-- Typed entities (person, place, list) are notes with a non-default note_type
-  plus type-specific columns; use the dedicated *_person / *_place / *_list
-  tools rather than create_note.
 - Tags are plain strings (no `#` prefix). Empty list clears tags; omit to leave
   unchanged on updates.
 - For optional integer FKs (project_id, milestone_id, parent_id), use 0 to mean
@@ -224,10 +219,9 @@ operator. "Works for one user" is not done.
 # write for read keys (default-deny), so a newly-added tool is locked down
 # until explicitly classified here.
 _READ_ONLY_TOOLS = frozenset({
-    "get_event", "get_note", "get_project", "get_rule", "get_rulebook",
+    "get_note", "get_project", "get_rule", "get_rulebook",
     "get_task", "get_milestone", "get_recent", "enter_project",
-    "list_events", "list_lists", "list_milestones", "list_notes",
-    "list_persons", "list_places", "list_projects", "list_rulebooks",
+    "list_milestones", "list_notes", "list_projects", "list_rulebooks",
     "list_rules", "list_tags", "list_tasks", "list_topics", "list_trash",
     "list_always_on_rules", "search",
     "get_system", "list_systems", "list_system_records",