feat: add ty type checking support and fix type issues

- Add ty.toml configuration with Django project root
- Add py.typed marker for type checking
- Fix type issues across codebase:
  - Add type ignore comments for redis.exceptions imports
  - Fix django.db.models.functions imports in utils
  - Fix getattr usage in accounts/forms
  - Remove unnecessary type annotations in dashboard/forms
- Configure ty to exclude migrations and respect ignore files
- All ty checks now pass (29 diagnostics -> 0)

dashboard_project/accounts/forms.py

@@ -30,7 +30,8 @@ class CustomUserChangeForm(forms.ModelForm):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         # Only staff members can change company and admin status
-        if not kwargs.get("instance") or not kwargs.get("instance").is_staff:
+        instance = kwargs.get("instance")
+        if not instance or not getattr(instance, "is_staff", False):
             if "company" in self.fields:
                 self.fields["company"].disabled = True
             if "is_company_admin" in self.fields: