perf(assets): convert images to webp and check asset paths

Convert 26 PNG/JPG assets to WebP: max 1600 px, q80, diagrams lossless.
src/assets shrinks from 8.3 MB to 4.2 MB.
Use me.jpg for og:image and twitter:image; some crawlers skip WebP.
Add scripts/check-assets.mjs to lint, so a wrong asset path fails lint,
not only at runtime.

src/app/layout/topbar/topbar.component.ts

@@ -5,6 +5,7 @@ import { MatIconModule } from '@angular/material/icon';
 import { MatButtonModule } from '@angular/material/button';
 import { MatMenuModule } from '@angular/material/menu';
 import { MatTooltipModule } from '@angular/material/tooltip';
+import { NgOptimizedImage } from '@angular/common';
 import { TranslatePipe } from '@ngx-translate/core';
 import { ThemeService } from '../../service/theme.service';
 import { LanguageService } from '../../service/language.service';
@@ -17,7 +18,7 @@ import {RouterConstants} from '../../constants/RouterConstants';
   imports: [
     RouterLink, RouterLinkActive,
     MatToolbarModule, MatIconModule, MatButtonModule, MatMenuModule, MatTooltipModule,
-    TranslatePipe, MatDivider
+    TranslatePipe, MatDivider, NgOptimizedImage
   ],
   templateUrl: './topbar.component.html',
   changeDetection: ChangeDetectionStrategy.Eager,