feat : sélecteur d'exercice sur l'onglet RTT de la fiche employé

Permet de consulter les exercices passés (table hebdomadaire RTT) en
réutilisant le pattern de l'onglet Congés. Plage bornée par
max(début historique contrat, RTT_START_DATE). Bouton + Payer les RTT
verrouillé sur exercices clos. Onglet masqué pour FORFAIT (inchangé).

Backend : rttStartDate désormais toujours exposé sur EmployeeRttSummary
pour que le sélecteur conserve sa borne lors de la navigation vers un
exercice passé. Le masquage existant des lignes Report continue de
fonctionner (comparaison mois-à-mois).

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

frontend/composables/useEmployeeRtt.ts

@@ -3,25 +3,94 @@ import type { EmployeeRttSummary } from '~/services/dto/employee-rtt-summary'
 import type { Employee } from '~/services/dto/employee'
 import { getEmployeeRttSummary, createRttPayment } from '~/services/employee-rtt-summary'
 
+export type RttYearOption = {
+  value: number
+  label: string
+}
+
 export const useEmployeeRtt = (employee: Ref<Employee | null>, reloadEmployee: () => Promise<void>) => {
   const rttSummary = ref<EmployeeRttSummary | null>(null)
   const isRttLoading = ref(false)
   const rttDataLoaded = ref(false)
+  const selectedRttYear = ref<number | null>(null)
+
+  // Exercice RTT : Juin (Y-1) → Mai (Y). Toujours, peu importe le type de contrat
+  // (l'onglet RTT est masqué pour les FORFAIT côté page).
+  const computeRttYearForDate = (date: Date): number =>
+    date.getMonth() >= 5 ? date.getFullYear() + 1 : date.getFullYear()
+
+  const currentRttYear = computed<number | null>(() => {
+    if (!employee.value) return null
+    return computeRttYearForDate(new Date())
+  })
+
+  const availableRttYears = computed<RttYearOption[]>(() => {
+    if (!employee.value || currentRttYear.value === null) return []
+    const current = currentRttYear.value
+
+    const startDates: string[] = []
+    for (const period of employee.value.contractHistory ?? []) {
+      if (period.startDate) startDates.push(period.startDate)
+    }
+    if (employee.value.entryDate) startDates.push(employee.value.entryDate)
+
+    let contractFloor = current
+    for (const raw of startDates) {
+      const date = new Date(`${raw.substring(0, 10)}T00:00:00`)
+      if (Number.isNaN(date.getTime())) continue
+      const rttYear = computeRttYearForDate(date)
+      if (rttYear < contractFloor) contractFloor = rttYear
+    }
+
+    // Hard floor : rttStartDate (env RTT_START_DATE) — pas d'historique avant.
+    let dataFloor: number | null = null
+    const dataStart = rttSummary.value?.rttStartDate
+    if (dataStart) {
+      const dataStartDate = new Date(`${dataStart.substring(0, 10)}T00:00:00`)
+      if (!Number.isNaN(dataStartDate.getTime())) {
+        dataFloor = computeRttYearForDate(dataStartDate)
+      }
+    }
+
+    const minYear = dataFloor !== null ? Math.max(contractFloor, dataFloor) : contractFloor
+
+    const years: RttYearOption[] = []
+    for (let y = current; y >= minYear; y -= 1) {
+      years.push({ value: y, label: `Juin ${y - 1} → Mai ${y}` })
+    }
+    return years
+  })
+
+  const initSelectedRttYear = () => {
+    if (selectedRttYear.value !== null) return
+    if (currentRttYear.value !== null) {
+      selectedRttYear.value = currentRttYear.value
+    }
+  }
 
   const loadRttData = async () => {
     if (!employee.value || isRttLoading.value) return
+    initSelectedRttYear()
+    if (selectedRttYear.value === null) return
     isRttLoading.value = true
     try {
-      const rttYear = new Date().getMonth() >= 5 ? new Date().getFullYear() + 1 : new Date().getFullYear()
-      rttSummary.value = await getEmployeeRttSummary(employee.value.id, rttYear)
+      rttSummary.value = await getEmployeeRttSummary(employee.value.id, selectedRttYear.value)
       rttDataLoaded.value = true
     } finally {
       isRttLoading.value = false
     }
   }
 
+  const setSelectedRttYear = async (year: number) => {
+    if (selectedRttYear.value === year) return
+    selectedRttYear.value = year
+    rttDataLoaded.value = false
+    await loadRttData()
+  }
+
   const resetLoaded = () => {
     rttDataLoaded.value = false
+    selectedRttYear.value = null
   }
 
   const submitRttPayment = async (month: number, base25Minutes: number, bonus25Minutes: number, base50Minutes: number, bonus50Minutes: number) => {
@@ -35,6 +104,10 @@ export const useEmployeeRtt = (employee: Ref<Employee | null>, reloadEmployee: (
     rttSummary,
     isRttLoading,
     rttDataLoaded,
+    selectedRttYear,
+    currentRttYear,
+    availableRttYears,
+    setSelectedRttYear,
     loadRttData,
     resetLoaded,
     submitRttPayment