fix(soft-delete): filter trashed rows across read/write paths

Drift-audit Group 3 (soft-delete lifecycle gaps). Trashed rows were
leaking into reads and being mutated/resurrected by writes:

- update SELECTs now exclude trashed rows: update_milestone,
  update_project, update_event, and get_milestone_in_project (the latter
  backs all four milestone routes). Mutating a trashed row silently
  persisted and reappeared on restore.
- MCP get_recent (notes/projects/events) and list_tags now filter
  deleted_at IS NULL, so trashed items stop surfacing in the agent's
  bootstrap context and tag counts.
- convert_task_to_note clears recurrence_rule + recurrence_next_spawn_at
  so a demoted note can't spawn children via the (now-live) sweep.
- caldav pull skips locally-trashed events (by caldav_uid) instead of
  resurrecting them via update or creating a duplicate live copy.
- trash _cascade now stamps the FULL sub-task subtree (iterative descent),
  not just direct children, so deeply nested sub-tasks restore as one
  batch. Test updated for the new descent query.

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

src/fabledassistant/services/trash.py

@@ -106,8 +106,21 @@ async def _cascade(session, user_id: int, etype: str, eid: int, batch: str, now)
         await _set(session, Note, [Note.user_id == user_id, Note.milestone_id == eid], batch, now)
         await _set(session, Milestone, [Milestone.user_id == user_id, Milestone.id == eid], batch, now)
     elif etype in ("note", "task"):
-        await _set(session, Note, [Note.user_id == user_id, Note.parent_id == eid], batch, now)  # sub-tasks
-        await _set(session, Note, [Note.user_id == user_id, Note.id == eid], batch, now)
+        # Stamp the entire sub-task subtree (not just direct children) so a
+        # deeply nested task and all its descendants trash/restore as one batch.
+        ids = [eid]
+        frontier = [eid]
+        while frontier:
+            children = (await session.execute(
+                select(Note.id).where(
+                    Note.user_id == user_id,
+                    Note.parent_id.in_(frontier),
+                    Note.deleted_at.is_(None),
+                )
+            )).scalars().all()
+            frontier = [c for c in children if c not in ids]
+            ids.extend(frontier)
+        await _set(session, Note, [Note.user_id == user_id, Note.id.in_(ids)], batch, now)
     elif etype == "event":
         await _set(session, Event, [Event.user_id == user_id, Event.id == eid], batch, now)
     elif etype == "rulebook":