Improve social media sharing and image optimization

Update meta tags in `index.html` for better Open Graph and Twitter Card compatibility, and update image URLs in `server/gallery-data.json`.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 1f7e7e89-a520-4970-9645-37daadc466dc
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: a2855efe-5aa8-492a-83ac-1f2ca8e1abca
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/f209e72a-0939-48fa-84fc-57854de71967/1f7e7e89-a520-4970-9645-37daadc466dc/ZApZ5Qi
Replit-Helium-Checkpoint-Created: true

client/index.html

@@ -12,9 +12,16 @@
     <meta property="og:site_name" content="Folx Music Television" />
     <meta property="og:url" content="https://www.folx.tv/" />
     <meta property="og:image" content="https://www.folx.tv/og-image.jpg" />
+    <meta property="og:image:secure_url" content="https://www.folx.tv/og-image.jpg" />
     <meta property="og:image:width" content="1200" />
     <meta property="og:image:height" content="630" />
     <meta property="og:image:type" content="image/jpeg" />
+    <meta property="og:image:alt" content="FOLX Network - Volksmusik & Schlager TV" />
+    <meta property="og:locale" content="de_DE" />
+    <meta name="twitter:card" content="summary_large_image" />
+    <meta name="twitter:title" content="Folx Music Television - Volksmusik & Schlager TV Sender" />
+    <meta name="twitter:description" content="FOLX TV – Ihr Fernsehsender für Volksmusik und Schlager. Musikvideos, Live-Shows und aktuelle Nachrichten." />
+    <meta name="twitter:image" content="https://www.folx.tv/og-image.jpg" />
     <meta name="robots" content="index, follow" />
     <link rel="canonical" href="https://www.folx.tv/" />
     <link rel="icon" type="image/png" href="/favicon.png" />