Implement internationalization support across components

- Integrated `next-intl` for toast messages and locale handling in various components, including `Providers`, `CanvasUserMenu`, and `CreditOverview`.
- Replaced hardcoded strings with translation keys to enhance localization capabilities.
- Updated `RootLayout` to dynamically set the language attribute based on the user's locale.
- Ensured consistent user feedback through localized toast messages in actions such as sign-out, canvas operations, and billing notifications.

lib/utils.ts

@@ -4,11 +4,3 @@ import { twMerge } from "tailwind-merge"
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs))
 }
-
-/** Credits / Preise: Werte sind Euro-Cent (siehe PRD, Manifest). */
-export function formatEurFromCents(cents: number) {
-  return new Intl.NumberFormat("de-DE", {
-    style: "currency",
-    currency: "EUR",
-  }).format(cents / 100)
-}