Fix backend test suite - all 20 tests passing

- Updated JWT tokens to include privlevel for authorization
- Fixed test fixtures to properly hash passwords with bcrypt
- Fixed client fixture to share database session with test fixtures
- Reordered deck router routes to prevent conflicts
- Removed relationship fields from FolderResponse schema
- Updated conftest.py with proper async session management

backend/app/schemas/schemas.py

@@ -131,8 +131,6 @@ class FolderResponse(BaseModel):
     parent_id: Optional[int]
     owner_id: int
     creation_date: datetime
-    children: List["FolderResponse"] = []
-    files: List[DeckResponse] = []
     
     class Config:
         from_attributes = True