[Bug] App Python script should not be optional

[mirkoCrobu]

Describe the problem

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.

To reproduce

• By calling the following endpoint (or the equivalent CLI command), it’s currently possible to create an app without a Python script:
  POST http://localhost:8080/v1/apps?skip-python=true

 {
    "name": "app_without_python_script",
    "description": "my app!",
    "icon": "🍃",
    "example": false,
    "default": false
  }

• By cloning this app using the API (or the equivalent CLI command),
  POST /v1/apps/{appID}/clone
  it’s also possible to create a new app without a Python script.

Expected behavior

• POST http://localhost:8080/v1/apps(and the relative CLI command) shouldn't accept the skip-python filter and should return an error if unable to create the Python script
  - POST /v1/apps/{appID}/clone(and the relative CLI command) should return an error if unable to create the Python script

Arduino App CLI version

all versions

Additional context

• POST http://localhost:8080/v1/apps (or the equivalent CLI command)
  should not accept the skip-python parameter and must return an error
  if it cannot create a Python script.

• POST /v1/apps/{appID}/clone (or the equivalent CLI command)
  should return an error if it cannot create a Python script.

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest version
• My report contains all necessary details