fix(ssr): fetch station config during server-side rendering

The isPlatformBrowser guard in App.ngOnInit() was blocking
stationConfig.load() on the server, so SSR always rendered with
DEFAULT_CONFIG (hardcoded colors, assets, content).

Two-part fix:
- main.server.ts: Add APP_INITIALIZER that blocks server rendering
  until station config is fetched from the API. Only runs on the
  server — is a no-op in the browser to avoid blocking the client.
- app.ts: Move stationConfig.load() before the isPlatformBrowser
  guard so ngOnInit also calls it on the server as a safety net.

This ensures SSR HTML contains real DB values (colors, hero icon,
station name, etc.) instead of build-time defaults — eliminating
the stale-asset flash reported by users.

src/main.server.ts

@@ -1,5 +1,4 @@
-import { APP_ID, APP_INITIALIZER, PLATFORM_ID } from '@angular/core';
-import { isPlatformBrowser } from '@angular/common';
+import { APP_ID, APP_INITIALIZER, isPlatformServer, PlatformId } from '@angular/core';
 import { bootstrapApplication, BootstrapContext } from '@angular/platform-browser';
 import { provideServerRendering, withRoutes } from '@angular/ssr';
 
@@ -28,9 +27,9 @@ const serverAppConfig = {
     {
       provide: APP_INITIALIZER,
       multi: true,
-      deps: [StationConfigService, PLATFORM_ID],
+      deps: [StationConfigService, PlatformId],
       useFactory: (svc: StationConfigService, platformId: object) => {
-        if (!isPlatformBrowser(platformId)) {
+        if (isPlatformServer(platformId)) {
           return () => svc.load().catch(() => {});
         }
         return () => {};