Center the page content and limit its width

Limit the maximum width of the page content to 1000px and center it using auto margins in index.css.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 8e9f2b36-ec9c-4acc-b19b-5304fa9790c5
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/8cc42625-c1f5-4e43-99bd-77f2c4dedee2/8e9f2b36-ec9c-4acc-b19b-5304fa9790c5/3f1nxbo

client/src/index.css

@@ -65,6 +65,8 @@
     background: linear-gradient(135deg, hsl(250, 50%, 15%) 0%, hsl(240, 30%, 25%) 50%, hsl(260, 40%, 20%) 100%);
     color: hsl(210, 40%, 98%);
     min-height: 100vh;
+    max-width: 1000px;
+    margin: 0 auto;
     /* iOS PWA optimizacije */
     -webkit-touch-callout: none;
     -webkit-user-select: none;