Polish: Tooltip & Animation Consistency

**Description**
Standardize tooltips and animations across the GUI:
- Smooth fade effects
- Consistent hover states
- Accessibility improvements

**Files**
- `src/scaleforge/gui/styles.kv`
- `src/scaleforge/gui/components/tooltips.py`

**Acceptance Criteria**
- [ ] 300ms fade animations
- [ ] WCAG-compliant contrast
- [ ] Mobile touch support