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/app.component.ts

@@ -1,5 +1,5 @@
 import { Component, HostListener } from '@angular/core';
-import { AsyncPipe, NgIf } from '@angular/common';
+import { AsyncPipe } from '@angular/common';
 import { RouterOutlet } from '@angular/router';
 import { SidebarComponent } from './sidebar/sidebar.component';
 import { SecondarySidebarComponent } from './shared/secondary-sidebar/secondary-sidebar.component';
@@ -13,15 +13,14 @@ import { VersionCheckerService } from './services/version-checker.service';
 @Component({
     selector: 'app-root',
     imports: [
-        RouterOutlet,
-        SidebarComponent,
-        SecondarySidebarComponent,
-        GlobalSearchComponent,
-        UpdateBannerComponent,
-        ConfirmDialogHostComponent,
-        AsyncPipe,
-        NgIf,
-    ],
+    RouterOutlet,
+    SidebarComponent,
+    SecondarySidebarComponent,
+    GlobalSearchComponent,
+    UpdateBannerComponent,
+    ConfirmDialogHostComponent,
+    AsyncPipe
+],
     templateUrl: './app.component.html',
     styleUrls: ['./app.component.scss']
 })