Replaced generic spinning character with a custom SVG eighth note
bouncing against four staff lines. Added note-bounce keyframe to
Tailwind config (0.6s ease-in-out infinite). More on-brand for a
music tool than a generic spinner.
- Added min-w-[140px] to prevent width change between states
- Border now always present (same color in both states), preventing 1px jump
- Text wrapped in truncate spans for overflow safety
- Spinning ♩ note preserved in loading state