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.

components/billing/pricing-cards.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import { useAuthQuery } from "@/hooks/use-auth-query";
+import { useTranslations } from "next-intl";
 import { Check } from "lucide-react";
 
 import { Badge } from "@/components/ui/badge";
@@ -13,18 +14,18 @@ import {
   TIER_MONTHLY_CREDITS,
 } from "@/lib/polar-products";
 import { toast } from "@/lib/toast";
-import { msg } from "@/lib/toast-messages";
 
 const TIER_ORDER = ["free", "starter", "pro", "max"] as const;
 
 export function PricingCards() {
+  const t = useTranslations('toasts');
   const subscription = useAuthQuery(api.credits.getSubscription);
   const currentTier = normalizeTier(subscription?.tier);
 
   async function handleCheckout(polarProductId: string) {
     toast.info(
-      msg.billing.redirectingToCheckout.title,
-      msg.billing.redirectingToCheckout.desc,
+      t('billing.redirectingToCheckoutTitle'),
+      t('billing.redirectingToCheckoutDesc'),
     );
     await authClient.checkout({ products: [polarProductId] });
   }