Fix base URL for subdirectory deployment on pages.civilytics.org

- Set vite.config.mjs base to '/crdc-demo/' so asset paths resolve correctly
  when served from a subdirectory (not root)
- Add favicon.svg in public/ folder
- Update index.html with correct absolute paths including /crdc-demo/ prefix

index.html

@@ -2,12 +2,13 @@
 <html lang="en">
   <head>
     <meta charset="UTF-8" />
-    <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
+    <link rel="icon" type="image/svg+xml" href="/crdc-demo/favicon.svg" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>CRDC Arrests API Demo — Civilytics</title>
   </head>
   <body>
     <div id="root"></div>
+    <!-- Vite injects the correct script tag with base-relative path -->
     <script type="module" src="/src/main.jsx"></script>
   </body>
 </html>