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/app/customers/page.tsx

@@ -1,7 +1,6 @@
 "use client";
 
 import {useState, useEffect, useMemo} from "react";
-import {useRouter} from "next/navigation";
 import {Button} from "@/components/ui/button";
 import {Input} from "@/components/ui/input";
 import {Card, CardContent} from "@/components/ui/card";
@@ -25,9 +24,9 @@ import {ArrowRight} from "lucide-react";
 import {NewCustomerModal} from "@/components/customers/modal/NewCustomerModal";
 import axios from "axios";
 import {Customer} from "@/services/customers/entities/customer";
+import Link from "next/link";
 
 export default function CustomersPage() {
-    const router = useRouter();
     const [customers, setCustomers] = useState<Customer[]>([]);
     const [search, setSearch] = useState("");
     const [loading, setLoading] = useState(true);
@@ -50,7 +49,7 @@ export default function CustomersPage() {
     }, []);
 
     const filtered = useMemo(() => {
-        if(customers.length === 0) return [];
+        if (customers.length === 0) return [];
 
         return customers.filter(
             (c) =>
@@ -143,13 +142,11 @@ export default function CustomersPage() {
                                                 <TableCell>{customer.city}</TableCell>
                                                 <TableCell>{new Date(customer.createdAt).toLocaleString()}</TableCell>
                                                 <TableCell>
-                                                    <Button
-                                                        variant="ghost"
-                                                        size="icon"
-                                                        onClick={() => router.push(`/customers/${customer.id}`)}
-                                                    >
-                                                        <ArrowRight className="w-4 h-4"/>
-                                                    </Button>
+                                                    <Link href={`/customers/${customer.id}`}>
+                                                        <Button variant="ghost" size="icon">
+                                                            <ArrowRight className="w-4 h-4"/>
+                                                        </Button>
+                                                    </Link>
                                                 </TableCell>
                                             </TableRow>
                                         ))}