feat: update theme management across the application; change default theme to 'light', disable system theme option, and add ThemeCard component in settings for enhanced user customization

app/settings/page.tsx

@@ -10,6 +10,7 @@ import {
   PasswordCard,
   ReconcileDateRangeCard,
   BackgroundCard,
+  ThemeCard,
 } from "@/components/settings";
 import { useBankingData } from "@/lib/hooks";
 import type { BankingData } from "@/lib/types";
@@ -127,6 +128,8 @@ export default function SettingsPage() {
 
         <PasswordCard />
 
+        <ThemeCard />
+
         <BackgroundCard />
 
         <ReconcileDateRangeCard />