Ajout des notification + page employé (#6)

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## Description de la PR

## Modification du .env

## Check list

- [ ] Pas de régression
- [ ] TU/TI/TF rédigée
- [ ] TU/TI/TF OK
- [ ] CHANGELOG modifié

Reviewed-on: #6
Co-authored-by: tristan <tristan@yuno.malio.fr>
Co-committed-by: tristan <tristan@yuno.malio.fr>

frontend/utils/contract.ts

@@ -0,0 +1,17 @@
+export const CONTRACT_NATURES = ['CDI', 'CDD', 'INTERIM'] as const
+
+export type ContractNature = (typeof CONTRACT_NATURES)[number]
+
+export const contractNatureLabel = (value?: ContractNature) => {
+  if (value === 'CDD') return 'CDD'
+  if (value === 'INTERIM') return 'Intérim'
+  return 'CDI'
+}
+
+export const requiresContractEndDate = (nature: ContractNature) => {
+  return nature === 'CDD' || nature === 'INTERIM'
+}
+
+export const isContractNature = (value: string): value is ContractNature => {
+  return (CONTRACT_NATURES as readonly string[]).includes(value)
+}