Migration Angular 20 -> 21 : fin de la migration securite (0 vulnerabilite npm)

- ng update @angular/core@21 @angular/cli@21 (corrige GHSA-jrmj-c5cx-3cw6, XSS SVG)
- Migration automatique des templates vers le control flow natif (@if/@for, 138 fichiers)
- Correction des 5 `track` invalides generes par la migration (trackBy a 1 argument
  -> track $index) + suppression des fonctions trackBy mortes
- TypeScript 5.9, zone.js 0.15 ; npm audit : 0 vulnerabilite

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/app/shared/chips-input/chips-input.component.html

@@ -1,10 +1,12 @@
 <div class="chips-wrapper">
-  <span class="chip" *ngFor="let tag of value; let i = index">
-    {{ tag }}
-    <button type="button" class="chip-remove" (click)="remove(i)" title="Retirer">
-      <lucide-icon [img]="X" [size]="12"></lucide-icon>
-    </button>
-  </span>
+  @for (tag of value; track tag; let i = $index) {
+    <span class="chip">
+      {{ tag }}
+      <button type="button" class="chip-remove" (click)="remove(i)" title="Retirer">
+        <lucide-icon [img]="X" [size]="12"></lucide-icon>
+      </button>
+    </span>
+  }
   <input
     type="text"
     class="chip-input"