fix: handle playlists with slashes in their names

[w3Abhishek]

Title

Fix: handle playlists with slashes in their names

Description

This PR fixes an issue where playlists containing slashes in their names would cause a FileNotFoundError when creating M3U files. The fix works by:

• Creates parent directories as needed before writing M3U files to prevent the FileNotFoundError

Related Issue

Fixes #2284

Motivation and Context

When a playlist name contained slashes like "init 3 - Neutral/Happy", the sanitize_string function would remove the slashes completely, resulting in filenames like "init 3 - NeutralHappy.m3u8". Additionally, if the directory structure didn't exist, the program would crash with a FileNotFoundError when trying to create the M3U file.

How Has This Been Tested?

Tested on Windows with playlist names containing slashes. The changes ensure that:

• M3U files are created successfully without errors

Screenshots (if appropriate)

Types of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the CONTRIBUTING document
• I have added tests to cover my changes
• All new and existing tests passed

[Copilot]

Pull Request Overview

This PR fixes a bug where playlists with slashes in their names would cause FileNotFoundError when creating M3U files. The fix ensures parent directories are created before writing the M3U file.

• Adds directory creation to handle nested paths from playlist names containing slashes
• Prevents FileNotFoundError when the directory structure doesn't exist

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[w3Abhishek]

Any updates on this @Silverarmor

[Silverarmor]

Please stop mentioning me on all platforms. I am human. I have more important things in life to prioritise and my work on spotDL is volunteer hours on top of that. I will get to it when I can, please be patient.
If you are worried about hacktoberfest, I will action the outstanding PRs during october and either merge them or tag as hacktoberfest-accepted.

[w3Abhishek]

Please stop mentioning me on all platforms. I am human. I have more important things in life to prioritise and my work on spotDL is volunteer hours on top of that. I will get to it when I can, please be patient. If you are worried about hacktoberfest, I will action the outstanding PRs during october and either merge them or tag as hacktoberfest-accepted.

Sorry for bothering. But, it's not just about Hacktoberfest. This is my first time contributing to this project and even after reading the Docs and Contributor guide I wasn't able to understand the exact process of contributing. I was only asking about this on Discord. Apologies again if that bothered you.