Add full language translation support and settings option

Integrates i18next and react-i18next for internationalization, adds German language support, and implements a language selection feature in the settings page.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ceced2fc-aa46-458d-ba87-ddd4b7bb1518
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/659922a9-0087-461c-90dd-6d9a58b81d4d/ceced2fc-aa46-458d-ba87-ddd4b7bb1518/un1X8jl

client/src/main.tsx

@@ -1,5 +1,6 @@
 import { createRoot } from "react-dom/client";
 import App from "./App";
 import "./index.css";
+import "./i18n/config";
 
 createRoot(document.getElementById("root")!).render(<App />);