fix: past days UX improvements and clear missed logic (#152)

- Render past days above 'Show past days' toggle when expanded
- Auto-scroll to today when expanding past days
- Remove blue hover color from past day dividers (use opacity instead)
- Fix 'All taken' logic: green only for manually taken doses
- Yellow styling stays for days with non-taken doses (even after dismissal)
- Warning icon disappears after 'Clear missed' (dismissed doses not counted)

frontend/src/test/pages/SchedulePage.test.tsx

@@ -94,6 +94,7 @@ const createMockContext = (overrides = {}) => ({
 	pastDays: [],
 	futureDays: [],
 	takenDoses: new Set(),
+	dismissedDoses: new Set(),
 	markDoseTaken: vi.fn(),
 	undoDoseTaken: vi.fn(),
 	coverageByMed: {},