Implement vim-style navigation and visual mode

- Add vim-style h key: closes folders and jumps to parent
- Implement stop() method in player for proper playback stopping
- Add space key to restart playback when stopped
- Add playlist color coding: green (playing), blue (paused), yellow (stopped)
- Fix n/p keys to preserve player state when switching tracks
- Implement vim-style visual mode with v key for multi-file selection
- Visual mode exits automatically on play/add actions
- Remove unused play_previous method
- Bump version to 0.1.7

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-player"
-version = "0.1.5"
+version = "0.1.7"
 edition = "2021"
 
 [dependencies]