Set dynamic theme color for PWA and Android status bar.

Added logic to update the theme-color meta tag dynamically based on the active theme. This improves the visual consistency of the application, particularly for PWA and Android users. Default theme color has also been updated in the configuration.

frontend/index.html

@@ -3,6 +3,7 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta name="theme-color" content="#000000" />
     <title>Cluedo Sheet</title>
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>