Add an artist listing page and improve SEO for various pages

Introduces a new `/kuenstler` page, API endpoint `/api/artists`, and enhances meta tags on `index.html` and for crawler requests on `/kuenstler`. Adds `KuenstlerPage.tsx` and updates `routes.ts` and `index.html`.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 401e2ec0-e00d-4f10-9d0e-60f3d479f9a5
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Event-Id: 69ee4fdb-c617-4cdd-b9f6-d3fab268d533
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/60d372ff-2c10-46c7-b01b-10c3435136b0/401e2ec0-e00d-4f10-9d0e-60f3d479f9a5/qFrskyV

client/index.html

@@ -19,6 +19,7 @@
     <script async src="https://fundingchoicesmessages.google.com/i/pub-4465464714854276?ers=1" nonce="temp-nonce"></script>
     <script nonce="temp-nonce">(function() {function signalGooglefcPresent() {if (!window.frames['googlefcPresent']) {if (document.body) {const iframe = document.createElement('iframe'); iframe.style = 'width: 0; height: 0; border: none; z-index: -1000; left: -1000px; top: -1000px;'; iframe.style.display = 'none'; iframe.name = 'googlefcPresent'; document.body.appendChild(iframe);} else {setTimeout(signalGooglefcPresent, 0);}}}signalGooglefcPresent();})();</script>
     <meta name="description" content="Folx TV - Nummer 1 in Europa für Volksmusik und Schlager. Video Streaming Plattform mit Musik, Unterhaltung und Live-Streaming." />
+    <meta name="keywords" content="Volksmusik, Schlager, Folx TV, Kastelruther Spatzen, Monika Martin, Oswald Sattler, Angela Wiedl, Die Grubertaler, Michael Hirte, Sašo Avsenik, Jonny Hill, Rosanna Rocci, Linda Feller, Julia Buchner, Melanie Payer, Marlena Martinelli, Musikvideo, Streaming, Volksmusik TV" />
     
     <!-- Google Search Console verification -->
     <meta name="google-site-verification" content="YcRvFNGnAbAnlhQvhODVJOaqHLVdOKnpCqk7oH-xeKE" />