feat: add tests for admin checks and error handling

- Introduced new tests for the `is_admin_async` function to verify correct behavior based on user roles.
- Added tests for error handling in the `error_handler` to ensure exceptions are logged and do not propagate.
- Enhanced test coverage for configuration settings by adding a test for parsing admin phone numbers from environment variables.
- Updated the `.cursorrules` file to include the use of a virtual environment for better dependency management.

.cursorrules

@@ -105,6 +105,7 @@
         "styling": "Not applicable",
         "testing_framework": "pytest",
         "build_tool": "setuptools",
+        "use_venv": ".venv",
         
         "deployment": {
             "environment": "Local machine",