feat: Add light/dark mode support with backend persistence

frontend/src/main.tsx

@@ -4,13 +4,16 @@ import './index.css'
 import App from './App.tsx'
 import { TooltipProvider } from "@/components/ui/tooltip"
 import { BrowserRouter } from "react-router-dom"
+import { ThemeProvider } from "./components/theme-provider"
 
 createRoot(document.getElementById('root')!).render(
   <StrictMode>
     <BrowserRouter>
-      <TooltipProvider>
-        <App />
-      </TooltipProvider>
+      <ThemeProvider>
+        <TooltipProvider>
+          <App />
+        </TooltipProvider>
+      </ThemeProvider>
     </BrowserRouter>
   </StrictMode>,
 )