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.

i18n/request.ts

@@ -0,0 +1,18 @@
+import { getRequestConfig } from 'next-intl/server';
+import { routing } from '../routing';
+
+export default getRequestConfig(async ({ requestLocale }) => {
+  let locale = await requestLocale;
+  const locales = routing.locales;
+  type Locale = (typeof locales)[number];
+
+  if (!locale || !locales.includes(locale as Locale)) {
+    locale = routing.defaultLocale;
+  }
+
+  return {
+    locale,
+    timeZone: 'Europe/Berlin',
+    messages: (await import(`../messages/${locale}.json`)).default,
+  };
+});