fix(ui): Cyrillic/Greek weights, html lang, weight normalisation (#1780)

Load Roboto 600/700 and DM Sans 700 so Cyrillic and Greek headings render
real semibold and bold faces instead of a synthetic bold, keep
<html lang> in step with the UI language, and move every font weight onto
the 400/500/600/700 scale (JetBrains Mono at 500 or lighter; the dashboard
LIVE badge now uses the interface font at 700).

Add the `styles:font-weights:validate` ratchet guard and its CI step. It
reads stylesheets much as Sass and the browser do (cascade, layers,
mixins, content blocks, `@extend`, `@at-root`, `:is()`/`:where()`,
keyframes) and lists what it deliberately does not trace in its header.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/app/app.component.spec.ts

@@ -1,9 +1,14 @@
+import { EventEmitter } from '@angular/core';
 import { ComponentFixture, TestBed, waitForAsync } from '@angular/core/testing';
 import { MatSnackBar } from '@angular/material/snack-bar';
 import { Router } from '@angular/router';
 import { Actions } from '@ngrx/effects';
 import { MockStore, provideMockStore } from '@ngrx/store/testing';
-import { TranslateService } from '@ngx-translate/core';
+import {
+    DefaultLangChangeEvent,
+    LangChangeEvent,
+    TranslateService,
+} from '@ngx-translate/core';
 import {
     EpgRuntimeBridgeService,
     EpgService,
@@ -150,7 +155,11 @@ describe('AppComponent', () => {
                 MockProvider(TranslateService, {
                     instant: jest.fn((key: string) => key),
                     setDefaultLang: jest.fn(),
+                    getDefaultLang: jest.fn(() => 'en'),
                     use: jest.fn(),
+                    onLangChange: new EventEmitter<LangChangeEvent>(),
+                    onDefaultLangChange:
+                        new EventEmitter<DefaultLangChangeEvent>(),
                 }),
                 // The real service imports locale chunks; the language switch
                 // is gated on it, so it must resolve deterministically here.