fix: production login error masking, resolve navbar hydration mismatch, and gracefully handle database render errors

shop/app/my-customers/page.tsx

@@ -2,6 +2,7 @@ export const dynamic = 'force-dynamic';
 import { redirect } from 'next/navigation'
 import Link from 'next/link'
 import { getEndCustomers } from '@/lib/actions/end-customers'
+import type { EndCustomer } from '@/lib/types'
 import { ArrowLeft, Building2, Plus, Edit2, AlertTriangle } from 'lucide-react'
 import { Button } from '@/components/ui/button'
 import { Card, CardContent } from '@/components/ui/card'
@@ -13,10 +14,20 @@ export default async function MyCustomersPage() {
   const { data: { user } } = await supabase.auth.getUser()
   if (!user) redirect('/auth/login')
 
-  const customers = await getEndCustomers()
+  let customers: EndCustomer[] = []
+  let fetchError: string | null = null
+  try {
+    customers = await getEndCustomers()
+  } catch (err: any) {
+    console.error("Error loading end customers:", err)
+    fetchError = err.message || "Es gab ein Problem beim Laden Ihrer Endkunden."
+  }
 
   // Anzahl Bestellungen pro Endkunde
-  const { data: orderCounts } = await supabase.from('orders').select('end_customer_id').not('end_customer_id', 'is', null);
+  const { data: orderCounts, error: orderError } = await supabase.from('orders').select('end_customer_id').not('end_customer_id', 'is', null);
+  if (orderError) {
+    console.error("Error loading order counts:", orderError)
+  }
 
   const countMap: Record<string, number> = {}
   ;(orderCounts ?? []).forEach(o => {
@@ -53,6 +64,12 @@ export default async function MyCustomersPage() {
           </Link>
         </div>
 
+        {fetchError && (
+          <div className="p-4 rounded-xl bg-red-500/10 border border-red-500/20 text-red-200 text-sm">
+            {fetchError}
+          </div>
+        )}
+
         {/* Keine Kunden */}
         {customers.length === 0 && (
           <Card className="glass-dark border-white/10">