Add always-visible player, play button on sidebar thumbnail, and GitHub link

- Player: Show minimal placeholder when no song is playing instead of hiding
- RightSidebar: Add play button overlay on cover art thumbnail
  - Hover to reveal play/pause button
  - Click anywhere on cover to play
  - Shows pause icon when song is currently playing
- SettingsModal: Add GitHub repo link for issues and feature requests

components/Player.tsx

@@ -75,7 +75,19 @@ export const Player: React.FC<PlayerProps> = ({
         return () => window.removeEventListener('keydown', handleKeyDown);
     }, [isFullscreen]);
 
-    if (!currentSong) return null;
+    // Show minimal player when no song is playing
+    if (!currentSong) {
+        return (
+            <div className="h-20 lg:h-24 bg-white dark:bg-black/95 backdrop-blur border-t border-zinc-200 dark:border-white/10 flex items-center justify-center z-50 transition-colors duration-300 shadow-[0_-4px_6px_-1px_rgba(0,0,0,0.1)] dark:shadow-none">
+                <div className="flex items-center gap-3 text-zinc-400 dark:text-zinc-600">
+                    <div className="w-10 h-10 lg:w-12 lg:h-12 rounded bg-zinc-200 dark:bg-zinc-800 flex items-center justify-center">
+                        <Play size={20} className="text-zinc-400 dark:text-zinc-600" />
+                    </div>
+                    <span className="text-sm font-medium">Select a song to play</span>
+                </div>
+            </div>
+        );
+    }
 
     const formatTime = (time: number) => {
         if (isNaN(time)) return "0:00";