feat(versions): include pin_kind/pin_label in backup export+restore

Both export paths emit pin_kind and pin_label per note_version row.
Restore reads them via .get() so backups predating the schema still
import cleanly (defaults to None → rolling).

src/fabledassistant/services/backup.py

@@ -150,6 +150,8 @@ async def export_full_backup() -> dict:
                 "title": nv.title,
                 "body": nv.body,
                 "tags": nv.tags or [],
+                "pin_kind": nv.pin_kind,
+                "pin_label": nv.pin_label,
                 "created_at": nv.created_at.isoformat(),
             }
             for nv in note_versions
@@ -314,6 +316,8 @@ async def export_user_backup(user_id: int) -> dict:
                 "title": nv.title,
                 "body": nv.body,
                 "tags": nv.tags or [],
+                "pin_kind": nv.pin_kind,
+                "pin_label": nv.pin_label,
                 "created_at": nv.created_at.isoformat(),
             }
             for nv in note_versions
@@ -605,6 +609,8 @@ async def _restore_v2(data: dict) -> dict:
                 title=nv_data.get("title", ""),
                 body=nv_data.get("body", ""),
                 tags=nv_data.get("tags", []),
+                pin_kind=nv_data.get("pin_kind"),
+                pin_label=nv_data.get("pin_label"),
                 created_at=_dt(nv_data.get("created_at")),
             )
             session.add(nv)