fix: use get_admin_db in access_share to handle cross-tenant session reads (public shares)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/endpoints/shares.py

@@ -9,6 +9,7 @@ from sqlalchemy.orm import joinedload
 from sqlalchemy.exc import IntegrityError
 
 from app.core.database import get_db
+from app.core.admin_database import get_admin_db
 from app.models.session import Session
 from app.models.session_share import SessionShare, SessionShareView
 from app.models.user import User
@@ -210,7 +211,7 @@ async def _get_optional_user(request: Request, db: AsyncSession) -> Optional[Use
 async def access_share(
     share_token: str,
     request: Request,
-    db: Annotated[AsyncSession, Depends(get_db)],
+    db: Annotated[AsyncSession, Depends(get_admin_db)],
 ):
     """Access a shared session via share token.