Data types in DB are returned as strings, crashes the API

[8de2fdb0]

Datase returns last_active_at as str.

Guess that is the same for all database Date types.

Traceback (most recent call last):
INFO:     10.89.2.53:52768 - "GET /v1/vector_stores HTTP/1.1" 500 Internal Server Error
  File "/app/main.py", line 187, in list_vector_stores
    last_active_at = int(row["last_active_at"].timestamp()) if row.get("last_active_at") else None
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'timestamp'