feat(search): add fuzzy search functionality with '/' trigger

Implement real-time fuzzy search for songs with the following features:
- Press '/' to enter search mode
- Fuzzy matching algorithm with scoring (exact > substring > fuzzy)
- Real-time filtering as user types
- Navigate filtered results with up/down arrows
- Press Enter to play selected song and exit search mode
- Press Esc to exit search mode
- UI updates show search query and filtered count
- All existing controls work normally outside search mode

The fuzzy search prioritizes exact matches, then substring matches,
then character sequence matches, making it easy to find songs quickly.

Author: coolcode