feat(seo): Phase 3 — preload LCP image and reduce APP_INITIALIZER blocking

- Add <link rel="preload"> for hero background image (LCP element) in index.html
- Remove blocking APP_INITIALIZER for config.json and station config loading
- Config loads now fire asynchronously in App.ngOnInit() (browser only)
- SSR/prerender renders instantly with default config — no network wait
- Improves LCP, Time to First Byte, and initial paint for SEO

src/app/app.ts

@@ -1,5 +1,6 @@
 import { Component, computed, effect, inject, OnInit, OnDestroy, PLATFORM_ID } from '@angular/core';
 import { isPlatformBrowser } from '@angular/common';
+import { HttpClient } from '@angular/common/http';
 import { RouterOutlet } from '@angular/router';
 import { NavbarComponent } from './navbar/navbar.component';
 import { MediaPlayerComponent } from './media-player/media-player.component';
@@ -7,6 +8,7 @@ import { FooterComponent } from './footer/footer.component';
 import { StructuredDataComponent } from './structured-data/structured-data.component';
 import { StationConfigService } from './services/station-config.service';
 import { SeoService } from './services/seo.service';
+import { loadAppConfigAsync } from './services/app-config.service';
 
 @Component({
   selector: 'app-root',
@@ -19,6 +21,7 @@ export class App implements OnInit, OnDestroy {
   private stationConfig = inject(StationConfigService);
   private seoService = inject(SeoService);
   private platformId = inject(PLATFORM_ID);
+  private http = inject(HttpClient);
 
   readonly hasStream = computed(() => {
     const cfg = this.stationConfig.config();
@@ -54,6 +57,12 @@ export class App implements OnInit, OnDestroy {
     // These DOM operations only run in the browser.
     if (!isPlatformBrowser(this.platformId)) return;
 
+    // Load runtime config.json and station config asynchronously in the
+    // background — do not block rendering. The app already renders with
+    // defaults from the SSR/prerendered HTML.
+    loadAppConfigAsync(this.http).catch(() => {});
+    this.stationConfig.load().catch(() => {});
+
     // Start watching router for automatic SEO metadata updates per route.
     this.seoService.watchRouter();
     // Handle the initial route (NavigationEnd already fired before ngOnInit).