AUTH-001: Update User Model with Base Fields

[lbedner]

Priority: High | Estimate: S

Add missing fields to base user model that all auth levels need:

• is_verified: bool - for email verification flow
• last_login: datetime | None - tracking

Files

• aegis/templates/.../app/models/user.py
• aegis/core/migration_generator.py (AUTH_MIGRATION spec)

Acceptance Criteria

• User model has is_verified and last_login fields
• Migration spec updated
• Login endpoint updates last_login on success