feat(leave) : align forfait CP N + display remaining workdays + N-1 absences exempt from presence

- LeaveRecapRowBuilder: forfait CP N now reflects remainingDays (acquis − pris depuis N) instead of the constant acquiredDays. Affects both PDF export and screen recap.
- Employee detail header: forfait label becomes "Forfait - 218 jours (X restants)" where X = 218 − presence days from Jan 1 to today (today included).
- New EmployeeLeaveSummary.presenceDaysToToday field, computed via the same logic as presenceDaysByMonth but capped at today.
- Forfait business rule: leaves attributed to N-1 stock no longer decrement presence days. Implemented by chronologically consuming an N-1 budget (= previousYearTakenDays) inside computePresenceDaysByMonth before counting any absence. Non-forfait unaffected (budget is 0).
- Doc updates: CLAUDE.md (forfait/N-1 rule), functional-rules.md (CP N forfait semantics).

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

frontend/composables/useEmployeeDetailPage.ts

@@ -10,10 +10,11 @@ export const useEmployeeDetailPage = () => {
 
   const showLeaveTab = computed(() => employee.value?.currentContractNature !== 'INTERIM')
   const showRttTab = computed(() => employee.value?.contract?.type !== CONTRACT_TYPES.FORFAIT)
+  const isForfait = computed(() => employee.value?.contract?.type === CONTRACT_TYPES.FORFAIT)
   const employeeContractWorkLabel = computed(() => {
     const contract = employee.value?.contract
     if (!contract) return '-'
-    if (contract.type === CONTRACT_TYPES.FORFAIT) return 'Forfait'
+    if (contract.type === CONTRACT_TYPES.FORFAIT) return 'Forfait - 218 jours'
     if (contract.weeklyHours !== null && contract.weeklyHours !== undefined) return `${contract.weeklyHours} heures`
     return contract.name || '-'
   })
@@ -55,6 +56,9 @@ export const useEmployeeDetailPage = () => {
         await bonus.loadBonusData()
       } else if (activeTab.value === 'observation') {
         await observation.loadObservationData()
+      } else if (isForfait.value && showLeaveTab.value) {
+        // Eager load: needed for the "X jours restants" header label on forfait employees.
+        await leave.loadLeaveData()
       }
     } finally {
       isLoading.value = false
@@ -63,6 +67,13 @@ export const useEmployeeDetailPage = () => {
 
   const contract = useEmployeeContract(employee, loadEmployee)
   const leave = useEmployeeLeave(employee, loadEmployee)
+  const forfaitRemainingDaysLabel = computed(() => {
+    if (!isForfait.value) return ''
+    const presence = leave.leaveSummary.value?.presenceDaysToToday
+    if (presence === undefined || presence === null) return ''
+    const remaining = 218 - presence
+    return ` (${remaining} restants)`
+  })
   const rtt = useEmployeeRtt(employee, loadEmployee)
   const mileage = useEmployeeMileage(employee, loadEmployee)
   const formation = useEmployeeFormation(employee, loadEmployee)
@@ -97,6 +108,7 @@ export const useEmployeeDetailPage = () => {
     showLeaveTab,
     showRttTab,
     employeeContractWorkLabel,
+    forfaitRemainingDaysLabel,
     ...contract,
     ...leave,
     ...rtt,