feat(frontend): design système - tokens, composants ui et restylage des pages

Centralise les couleurs/rayons/espacements dispersés en dur dans chaque page
(login, change-password, dashboard) en tokens CSS partagés, ajoute un petit
set de composants standalone réutilisables (ev-button, ev-card, ev-alert,
ev-badge) et intègre le logo EnerVision en en-tête des pages ainsi que dans
Swagger/ReDoc côté backend.

Refs #91

apps/frontend/src/app/features/dashboard/dashboard.ts

@@ -9,16 +9,26 @@ import { SiteLoadChart } from '../../shared/components/site-load-chart/site-load
 import { AlertsService } from '../../core/services/alerts.service';
 import { AuthService } from '../../core/services/auth.service';
 import { StatsSummary } from '../../shared/models/stats.model';
-import { Alert } from '../../shared/models/alert.model';
+import { Alert, AlertSeverity } from '../../shared/models/alert.model';
+import { Card } from '../../shared/components/ui/card/card';
+import { Alert as EvAlert } from '../../shared/components/ui/alert/alert';
+import { Badge, BadgeTone } from '../../shared/components/ui/badge/badge';
 
 const REFRESH_INTERVAL_MS = 10000;
 const UNAVAILABLE_MESSAGE =
   'Données indisponibles, les valeurs affichées datent du dernier relevé.';
 
+const TON_PAR_SEVERITE: Record<AlertSeverity, BadgeTone> = {
+  low: 'success',
+  medium: 'warning',
+  high: 'danger',
+  critical: 'danger',
+};
+
 @Component({
   selector: 'app-dashboard',
   standalone: true,
-  imports: [DecimalPipe, ConsumptionGauge, SiteLoadChart],
+  imports: [DecimalPipe, ConsumptionGauge, SiteLoadChart, Card, EvAlert, Badge],
   templateUrl: './dashboard.html',
   styleUrl: './dashboard.scss',
 })
@@ -54,6 +64,10 @@ export class Dashboard implements OnInit {
       });
   }
 
+  badgeToneForSeverity(severity: AlertSeverity): BadgeTone {
+    return TON_PAR_SEVERITE[severity];
+  }
+
   onLogout(): void {
     this.auth.logout().subscribe({
       next: () => this.router.navigate(['/login']),