UI improvements: update favicon, reorder WordCard buttons, style logo, and refine color scheme

- Add custom favicon.ico to replace default Vite icon
- Reorder WordCard action buttons (Dodaj on left, Info on right)
- Add white circular background to sidebar logo for better visibility
- Update CSS color variables to use proper indigo color scheme with HSL values

packages/frontend/index.html

@@ -2,7 +2,7 @@
 <html lang="hr">
   <head>
     <meta charset="UTF-8" />
-    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+    <link rel="icon" type="image/x-icon" href="/favicon.ico" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <link rel="preconnect" href="https://fonts.googleapis.com" />
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />