refactor: remove skeleton toggle/shortcut feature from control server

show_skeleton is now managed by the Plasma wallpaper config directly,
so the server no longer needs toggle-skeleton, set-shortcut endpoints,
pynput hotkey listener, or the show_skeleton field in /current.
Also fixes unclosed file handle in the /art handler.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

luz-musica.py

@@ -139,7 +139,8 @@ class ControlHandler(BaseHTTPRequestHandler):
                 return
             try:
                 if art_url.startswith("file://"):
-                    body = open(art_url[7:], "rb").read()
+                    with open(art_url[7:], "rb") as f:
+                        body = f.read()
                     ctype = "image/png" if art_url.endswith(".png") else "image/jpeg"
                 else:
                     resp = requests.get(art_url, timeout=5)