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/notes.py

@@ -384,6 +384,10 @@ async def convert_task_to_note(user_id: int, note_id: int) -> Note:
         note.status = None
         note.priority = None
         note.due_date = None
+        # A plain note is not a task and must not recur — clear the rule and
+        # any armed spawn timestamp so the recurrence sweep never picks it up.
+        note.recurrence_rule = None
+        note.recurrence_next_spawn_at = None
         note.updated_at = datetime.now(timezone.utc)
         await session.commit()
         await session.refresh(note)