feat(auth): define Default/Local owner contract (#5795)

* feat(auth): define default local owner contract

* test(auth): harden default local owner matrix

---------

Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>

routes/assistant_routes.py

@@ -16,7 +16,7 @@ from pydantic import BaseModel
 
 from core.database import SessionLocal, CrewMember, ScheduledTask
 from src.auth_helpers import get_current_user
-from core.auth import RESERVED_USERNAMES
+from src.owner_identity import REQUEST_SENTINEL_OWNERS
 from src.task_scheduler import compute_next_run
 
 
@@ -90,11 +90,12 @@ def setup_assistant_routes(task_scheduler) -> APIRouter:
     # check-in tasks seeded. Hitting any /assistant route under one of these
     # used to seed a full CrewMember + Morning/Midday/Evening tasks under that
     # owner, which then double-fired alongside the real user's check-ins.
-    # RESERVED_USERNAMES covers the same set; the `not owner` guard handles "".
+    # REQUEST_SENTINEL_OWNERS covers request-only identities; Default/Local is a
+    # reserved login name but remains a valid storage owner.
 
     async def _get_or_create(owner: str) -> CrewMember:
         """Return the per-owner assistant CrewMember, creating it on demand."""
-        if not owner or owner in RESERVED_USERNAMES:
+        if not owner or owner in REQUEST_SENTINEL_OWNERS:
             raise HTTPException(status_code=400, detail=f"Cannot seed assistant for {owner!r}")
         db = SessionLocal()
         try: