fix(seo): add RouterLinkWithHref imports + default social media fields

- Import RouterLinkWithHref in footer and events components (required for queryParams binding on <a>)
- Add social media fields to DEFAULT_CONFIG in station-config.service.ts

src/app/services/station-config.service.ts

@@ -32,6 +32,11 @@ const DEFAULT_CONFIG: StationConfig = {
   play_store_icon_url: '',
   play_store_url: '',
   app_store_embed_html: '',
+  // Social media
+  social_facebook: '',
+  social_twitter: '',
+  social_instagram: '',
+  social_youtube: '',
   // Page content
   hero_subtitle: 'Your community-powered, nonprofit radio station — bringing music, stories, and connection to the mountain towns and beyond since 1987.',
   about_intro: 'For nearly four decades, KMountain Flower Radio has been the voice of our community — a nonprofit, listener-supported radio station dedicated to music, local news, and the stories that bind mountain towns together.',