fix: Use TypeConflitPlanification and GraviteConflict enums instead of strings

app/(main)/planning/calendrier/page.tsx

@@ -23,6 +23,7 @@ import { Divider } from 'primereact/divider';
 import { chantierService } from '../../../../services/api';
 import { formatDate, formatDateTime } from '../../../../utils/formatters';
 import type { Chantier, PlanningEvent as PlanningEventType, Equipe, Materiel, Employe, PlanningConflict } from '../../../../types/btp';
+import { TypeConflitPlanification, GraviteConflict } from '../../../../types/btp';
 
 interface PlanningCalendrierEvent {
     id: string;
@@ -303,11 +304,11 @@ const CalendrierPlanningPage = () => {
                 if (event1.start < event2.end && event1.end > event2.start) {
                     conflicts.push({
                         id: `conflict-${i}-${j}`,
-                        type: 'CHEVAUCHEMENT_HORAIRES',
+                        type: TypeConflitPlanification.CHEVAUCHEMENT_HORAIRES,
                         description: `Conflit horaire entre "${event1.title}" et "${event2.title}"`,
                         events: [event1, event2] as any,
                         ressources: [],
-                        gravite: 'ATTENTION',
+                        gravite: GraviteConflict.ATTENTION,
                         suggestions: [
                             'Décaler l\'un des événements',
                             'Réduire la durée des événements',