Update site URLs to use the 'www' subdomain across the application

- Changed the site URL in index.html, router, and server routes from 'https://ypchat.net' to 'https://www.ypchat.net' for consistency and improved SEO.
- Updated related meta tags and constants to reflect the new URL structure.

These changes ensure a unified domain reference throughout the application.

client/src/router/index.js

@@ -4,7 +4,7 @@ import PartnersView from '../views/PartnersView.vue';
 import MockupView from '../views/MockupView.vue';
 import FeedbackView from '../views/FeedbackView.vue';
 
-const SITE_URL = 'https://ypchat.net';
+const SITE_URL = 'https://www.ypchat.net';
 const DEFAULT_IMAGE = `${SITE_URL}/static/favicon.png`;
 
 const homeSchema = {