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/dashboard/management/commands/create_test_data.py

@@ -83,7 +83,7 @@ class Command(BaseCommand):
             ChatSession.objects.all().delete()
 
         # Parse sample CSV
-        with open(sample_path, "r") as f:
+        with open(sample_path) as f:
             reader = csv.reader(f)
             header = next(reader)  # Skip header