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/data_integration/admin.py

@@ -52,10 +52,8 @@ class ExternalDataSourceAdmin(admin.ModelAdmin):
                 status,
             )
         else:
-            return format_html(
-                '<span style="color: white; background-color: orange; padding: 3px 8px; border-radius: 10px;">{}</span>',
-                status,
-            )
+            style = "color: white; background-color: orange; padding: 3px 8px; border-radius: 10px;"
+            return format_html(f'<span style="{style}">{{}}</span>', status)
 
     @admin.display(description="Actions")
     def refresh_action(self, obj):