feat : migrate filter/form UI to @malio/layer-ui + fix hours/calendar contract scoping

- Add @malio/layer-ui as Nuxt layer (extends in nuxt.config.ts)
- Migrate site/employee/contract filters to MalioSelectCheckbox / MalioInputText / MalioSelect on employees, calendar and hours screens
- Migrate absence drawer selects + submit button to Malio (MalioSelect + MalioButton)
- Migrate calendar "Ajouter une absence" / "Imprimer" actions to MalioButton
- Drop now-unused EmployeeNameFilterInput and SiteFilterSelector components
- Hours day view: resolve contract nature at selected date (WorkHourDayContext.contractNature) instead of employee.currentContractNature (today-based); fixes interim contracts showing as CDI when mission ended
- Calendar: hide employees whose contract periods do not intersect the displayed month
- Layout: scrollbar-gutter:stable on <main> to avoid horizontal shift when dropdowns open
- Update functional-rules.md, in-app documentation, CLAUDE.md to match

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/composables/useDriverHoursPage.ts

@@ -417,6 +417,10 @@ export const useDriverHoursPage = () => {
     return date.toLocaleDateString('fr-FR', { day: '2-digit', month: '2-digit', year: 'numeric', hour: '2-digit', minute: '2-digit' })
   }
 
+  const getRowContractNature = (employeeId: number): 'CDI' | 'CDD' | 'INTERIM' | null => {
+    return dayContextByEmployeeId.value.get(employeeId)?.contractNature ?? null
+  }
+
   const hasContractAtSelectedDate = (employeeId: number) => {
     const dayRow = dayContextByEmployeeId.value.get(employeeId)
     if (!dayRow) return true
@@ -982,6 +986,7 @@ export const useDriverHoursPage = () => {
     getRowMetrics,
     getRowAbsenceLabel,
     getRowAbsenceStyle,
+    getRowContractNature,
     getRowUpdatedAt,
     openAbsenceDrawer,
     submitAbsence,