Libre.fm support

[boldandbrad]

Describe the problem
Users who prefer Libre.fm over last.fm cannot use spin, limiting the app's accessibility for those who want an open-source scrobbling alternative.

Describe the solution you'd like
Add Libre.fm as an alternative scrobbling backend:

• Add --service flag to specify lastfm or librefm on profile creation
• Store service details per profile
• Use Libre.fm's compatible API (similar to last.fm)
• Add profile's service alongside profile name wherever it is printed

Example:

spin profile add --service librefm myusername

Describe alternatives you've considered
None - Libre.fm is the primary open-source scrobbling service alternative.

Additional context/considerations

• Libre.fm API is compatible with last.fm scrobbling API
• Need separate API keys for Libre.fm
• Keep things simple: only one service per profile