Switch to pure python library for dbus

[allhailwesttexas]

Using the CLI requires system-level dbus packages to be installed, which vary by distro and can sometimes cause problems even when installed if trying to run spotifycli in an isolated env (like installing with pipx or uv). To sidestep this issue, switch to using jeepney, a pure python implementation of the dbus interface. Since it is lower level, the logic ends up a little bit more complex. This could be improved, but since the changes are still quite small it didn't feel worthwhile at this point.

Closes #53.

I have written a script to test the output of all the supported CLI endpoints, but writing stable tests would require a bigger refactor, so I won't add it to the commit, I'll just paste it in here (since it doesn't rely on mocking the dbus response and instead requires exact setup).

import io
import sys
from contextlib import redirect_stdout
from unittest.mock import patch

from spotifycli.spotifycli import main

def test_main():

    cases = (
        ("--status", "Tindersticks - Travelling Light\n"),
        ("--statusshort", "Tindersticks - Travelling...\n"),
        ("--statusposition", "Tindersticks - Travelling Light (00:07/04:51)\n"),
        ("--song", "Travelling Light\n"),
        ("--songshort", "Travelling...\n"),
        ("--artist", "Tindersticks\n"),
        ("--artistshort", "Tindersticks\n"),
        ("--album", "Tindersticks\n"),
        ("--position", "(00:07/04:51)\n"),
        ("--playbackstatus", "▮▮\n"),
        ("--lyrics", "lyrics not found\n"),
        ("--arturl", "https://i.scdn.co/image/ab67616d0000b273cdd1aabdf50a42ca4556d31d\n"),
    )

    for flag, expected in cases:
        f = io.StringIO()
        with redirect_stdout(f), patch.object(sys, 'argv', ['spotifycli', '--client', 'spotify', flag]):
            main()
            result = f.getvalue()
            assert result == expected

[pwittchen]

Thanks for the PR!