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.

lib/auth-server.ts

@@ -1,5 +1,7 @@
 import { convexBetterAuthNextJs } from "@convex-dev/better-auth/nextjs";
 
+import { api } from "@/convex/_generated/api";
+
 export const {
   handler,              // Route Handler für /api/auth/*
   preloadAuthQuery,     // SSR: Query mit Auth vorladen
@@ -17,3 +19,8 @@ export const {
     isAuthError: (error) => /auth/i.test(String(error)),
   },
 });
+
+/** Aktueller User für SSR (z. B. Sentry `setUser`), oder `null`. */
+export async function getAuthUser() {
+  return fetchAuthQuery(api.auth.safeGetAuthUser, {});
+}