Standalone Mode

We can finally call ourselves a "music player" now, heh.

• New: Builtin MPD server orchestration for a normal music player-like experience. This is achieved by running mpd as a subprocess with a managed configuration file and private state, DB and playlist paths. Connection to said subprocess is done via a managed Unix socket so as to avoid taking up any TCP port on your system. As long as you have mpd installed locally and in $PATH, Euphonica can borrow it. This does not hijack your existing systemd service. Euphonica only shares the executable and runs its own instance.
• New: A (relatively) rich GUI-based MPD configurator for its own instance. Does not support import/export yet as we only implement a subset of the whole config language (many things are unnecessary for our intents and purposes).
• Change: more pages added to the onboarding guide to help new users pick a mode (Standalone or Client).

You're invited to read the notes & view screenshots in #354 for more information.

Notes to package maintainers: Please add MPD as a dependency from now on, and spin off an MPD-less package with -client or some other suitable prefix (see Arch Linux precedent).

Notes to AUR users: If you've been using the euphonica package by supermario, you should be set. If you're using euphonica-git, the next update will install mpd. Should you want to keep it off your system (for example if you're exclusively connecting to a remote MPD server), please switch to euphonica-client-git.

Euphonica remains GPL3.0-licensed as it and MPD are still separate programmes communicating via a pipe (see the mere aggregation clause).

Visualiser

• Change: Visualiser now uses asymmetric sliding-window averaging to capture transients better.
• Fix: incorrect FIFO visualiser behaviour.

Other changes

• Change: rotating artwork now uses trilinear filtering for a less noisy look.
• Fix: lyrics deletion now works correctly.
• Fix: a big memory leak on closing window in background mode. Long-lived Euphonica instances should no longer gobble up RAM now.
• Fix: various console warnings regarding UI elements, might also fix crashes on Macs running Asahi Linux.

Pull Requests

• Redesign onboarding library type selection by @aaravrav in #355
• Add Nix flake by @aaravrav in #356
• Run cargo fmt by @catap in #359
• Fix a few issues by @htkhiem in #361
• fix: correct minimized option flags by @aaravrav in #362
• fix: seekbar GTK criticals by @aaravrav in #363
• fix: handle missing durations in LRCLIB results by @aaravrav in #364
• fix: apply upstream webp workaround to flake dev shell by @aaravrav in #365
• feat: use trilinear filtering for rotating artwork by @aaravrav in #366
• docs: update nixpkgs package maintainers by @aaravrav in #367
• fix: preserve preferences page layout manager by @aaravrav in #369
• fix: fit artist header at minimum window width by @aaravrav in #370
• fix: size marquee labels correctly by @aaravrav in #371
• Add automatic MPD server management by @htkhiem in #354

Full Changelog: v0.99.7-beta-1...v0.99.8-beta