Refactor navigation structure and API routes

- Centralize user menu, sidebar items, and breadcrumb logic.
- Map consistent API endpoints in `customerRoutes`.
- Replace inline route definitions with reusable constants.
- Refactor auth configuration file location.
- Improve `<Link>` usage to replace static `<a>` elements.
- Adjust sidebar and dropdown components to use dynamic navigation configurations.

internal_frontend/lib/api/serverCall.ts

@@ -1,6 +1,6 @@
 // lib/callBackendApi.ts
 import {getServerSession} from "next-auth";
-import {authOptions} from "@/lib/auth/authOptions";
+import {authOptions} from "@/lib/api/auth/authOptions";
 
 export async function serverCall(
     path: string,