feat: Implement song search and refactor song browser

[tomast1337]

This PR introduces a new song search functionality and refactors the song browsing routes.

Key changes include:

• Implemented a new feature to allow users to search for songs.
• Merged the song-browser routes into the main song controller to improve code organization.
• Fixed several linting problems identified in the codebase.

[tomast1337]

Bentroen:

This type of method is a bit weird, maybe? (A specific getSong for the 'my songs' page)
Because a more generic method with a ?user= parameter, which, when left blank, would return the songs of the logged-in user, would solve it.
It practically duplicates the getSongByPage.

[Bentroen]

I believe this PR was superseded by #54 and #59 - is there anything else from here left to implement? :)
If not, we might be good closing this one!