feat: integrate Sentry for error tracking and enhance user notifications

- Added Sentry integration for error tracking across various components, including error boundaries and user actions.
- Updated global error handling to capture exceptions and provide detailed feedback to users.
- Enhanced user notifications with toast messages for actions such as credit management, image generation, and canvas exports.
- Improved user experience by displaying relevant messages during interactions, ensuring better visibility of system states and errors.

components/init-user.tsx

@@ -3,7 +3,9 @@
 import { authClient } from "@/lib/auth-client";
 import { useMutation, useQuery } from "convex/react";
 import { api } from "@/convex/_generated/api";
-import { useEffect } from "react";
+import { useEffect, useRef } from "react";
+import { toast } from "@/lib/toast";
+import { msg } from "@/lib/toast-messages";
 
 /**
  * Initialisiert die Credit-Balance für neue User.
@@ -17,16 +19,27 @@ export function InitUser() {
     session?.user ? {} : "skip"
   );
   const initBalance = useMutation(api.credits.initBalance);
+  const initStartedRef = useRef(false);
 
   useEffect(() => {
     if (
-      session?.user &&
-      balance &&
-      balance.balance === 0 &&
-      balance.monthlyAllocation === 0
+      !session?.user ||
+      !balance ||
+      balance.balance !== 0 ||
+      balance.monthlyAllocation !== 0
     ) {
-      initBalance();
+      return;
     }
+    if (initStartedRef.current) return;
+    initStartedRef.current = true;
+
+    void initBalance()
+      .then(() => {
+        toast.success(msg.auth.initialSetup.title, msg.auth.initialSetup.desc);
+      })
+      .catch(() => {
+        initStartedRef.current = false;
+      });
   }, [session?.user, balance, initBalance]);
 
   return null;