Remove callApi, refactor API integrations, and adjust error handling

- Delete unused `callApi` utility and related imports across components.
- Replace `callApi` with direct `fetch` usage in `validateCustomer` and `addCustomer`.
- Update `customerRoutes` to include `/api` prefix for consistency.
- Refactor `useErrorHandler` to ensure comprehensive state management during errors.
- Improve `ErrorBoundary` component text for better clarity in fallback UI.
- Align `CustomersPage` logic with `useCallback` for optimized dependency management.

internal_frontend/components/error-boundary.tsx

@@ -99,9 +99,9 @@ function ErrorDialog({error, onReset, open}: ErrorDialogProps) {
         }}>
             <DialogContent className="sm:max-w-md">
                 <DialogHeader>
-                    <DialogTitle>Ein Fehler ist aufgetreten</DialogTitle>
+                    <DialogTitle>Uncaught Error!</DialogTitle>
                     <DialogDescription>
-                        Es ist ein unerwarteter Fehler aufgetreten. Bitte versuchen Sie es erneut.
+                        Es ist ein unerwarteter Fehler aufgetreten.
                     </DialogDescription>
                 </DialogHeader>
 
@@ -128,7 +128,16 @@ function ErrorDialog({error, onReset, open}: ErrorDialogProps) {
 
 // Hook for handling async errors
 export function useErrorHandler() {
+    const [errorState, setErrorState] = React.useState();
+
+    console.log('Current state:', errorState);
+
     return React.useCallback((error: unknown) => {
         console.error("Async error caught:", error);
+
+        // Trigger a re-render that will throw the error and be caught by the error boundary 
+        setErrorState(() => {
+            throw error instanceof Error ? error : new Error(String(error));
+        });
     }, []);
 }