style(storybook): group form, selection and date picker story pages

- Button page shows Toggle; new Selection Controls page compares Checkbox,
  Radio Group and Switch states (specimens moved to *-examples.tsx)
- Date Picker page includes Calendar; Combobox, Input and Slider layouts
  (Korean slider labels) tidied
- Absorbed representative Stories keep their IDs as verification Stories
- Component docs updated to the new representative pages

docs/components/calendar.md

@@ -10,7 +10,7 @@
 | 구현 상태 | 구현 완료 (현재 HM 규격) |
 | 기준일 | 2026-10-02 |
 | 기반 | shadcn/ui Calendar = **react-day-picker v10** |
-| 대표 Story | `Components/Search & Date/Calendar` → `All` (이름 "Calendar") |
+| 대표 Story | `Components/Search & Date/Date Picker` → `All`의 "Calendar · …" 섹션(사이드바 `날짜 선택`). 기존 `Components/Search & Date/Calendar` → `All`(`components-search-date-calendar--all`)은 URL 직접 접근용으로 유지(사이드바 숨김) |
 | 보류 | 아래 §11 |
 
 ## 2. 적용 근거