Ajoute projet et migration milestone

Signed-off-by: Gato <cedric@goutailler-olivier.fr>

src/app/milestones/milestone-detail/milestone-detail.html

@@ -11,6 +11,8 @@
         <button type="button" class="btn btn-outline-secondary btn-sm" (click)="toggleMoreMenu()">···</button>
         @if (moreMenuOpen) {
           <div class="more-menu dropdown-menu show">
+            <button type="button" class="dropdown-item" (click)="openMigrate()">Migrer vers un autre projet</button>
+            <div class="dropdown-divider"></div>
             <button type="button" class="dropdown-item text-danger" (click)="deleteMilestone()">Supprimer</button>
           </div>
         }
@@ -22,6 +24,40 @@
   </div>
 </div>
 
+<!-- Panneau de migration -->
+@if (showMigratePanel) {
+  <div class="migrate-panel mb-3">
+    <div class="migrate-title">Migrer « {{ milestone.name }} » vers un autre projet</div>
+    @if (availableProjects.length === 0) {
+      <p class="migrate-empty">Aucun autre projet disponible.</p>
+    } @else {
+      <select
+        class="migrate-select form-select form-select-sm"
+        [(ngModel)]="selectedMigrateProjectId"
+        name="migrateProject"
+      >
+        <option [ngValue]="null" disabled>Sélectionner un projet…</option>
+        @for (project of availableProjects; track project.id) {
+          <option [ngValue]="project.id">{{ project.name }}</option>
+        }
+      </select>
+    }
+    <div class="migrate-actions">
+      <button
+        type="button"
+        class="btn btn-sm btn-primary"
+        (click)="confirmMigrate()"
+        [disabled]="selectedMigrateProjectId === null"
+      >
+        Confirmer la migration
+      </button>
+      <button type="button" class="btn btn-sm btn-outline-secondary" (click)="cancelMigrate()">
+        Annuler
+      </button>
+    </div>
+  </div>
+}
+
 <!-- Titre -->
 <div class="card shadow-sm mb-3">
   <div class="card-body py-2">