fix(packaging): compile binary as qbz instead of qbz-nix

Add [[bin]] section to Cargo.toml so cargo produces target/release/qbz
directly. Update all packaging references (workflows, PKGBUILD, Flatpak
manifest, AUR desktop file) to use the new binary name. This fixes DEB
and RPM packages installing the binary as /usr/bin/qbz-nix instead of
/usr/bin/qbz.

packaging/aur/qbz.desktop

@@ -6,6 +6,6 @@ Type=Application
 Icon=qbz
 Categories=AudioVideo;Audio;Music;Player;
 Terminal=false
-StartupWMClass=qbz-nix
+StartupWMClass=QBZ
 Keywords=music;audio;qobuz;hifi;streaming;audiophile;
 MimeType=x-scheme-handler/qbz;x-scheme-handler/qobuzapp;