[BUG][LOW] Fragile date parsing in User.from_dict with no timezone handling

[kambiz-aghaiepour]

Description

The User.from_dict method parses dates with a fragile string comparison that only matches one specific format and has no timezone handling:

# src/quads/server/models.py:455-459
for attr in ['last_login', 'first_login']:
    if data.get(attr):
        if isinstance(data[attr], str):
            if data[attr] != '1970-01-01T00:00:00':
                setattr(self, attr, datetime.fromisoformat(data[attr]))
            else:
                setattr(self, attr, None)

Impact

• Hardcoded epoch comparison is fragile and format-specific
• No timezone handling on parsed datetimes
• Any deviation in date format causes unexpected behavior

Recommended Fix

Use a proper date parsing library with timezone handling (e.g., dateutil.parser.parse) and handle the epoch/null case more robustly.