remove no-python option for creating app

[mirkoCrobu]

Motivation

closes #113

Currently, an app’s Python script is handled as an optional module by design.
This assumption is incorrect: every App must always include a Python script.

Change Description

• Identify all the logic that treats the Python script as optional and make it mandatory.
• Ensure proper handling of cases where the script cannot be created, including related error paths.
• Update existing tests to reflect this change, or add missing ones if needed.
• Update the createApp endpoint by removing the skipPython flag, and revise the OpenAPI spec and e2e tests accordingly.

Additional Notes

Reviewer checklist

• PR addresses a single concern.
• PR title and description are properly filled.
• Changes will be merged in main.
• Changes are covered by tests.
• Logging is meaningful in case of troubleshooting.

[lucarin91]

Can you please fix the tests?