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">

shop/components/NavbarClient.tsx

@@ -21,6 +21,11 @@ export function NavbarClient({ user, role = "partner" }: NavbarClientProps) {
   const [userRole, setUserRole] = useState<string>(role);
   const [isMobileMenuOpen, setIsMobileMenuOpen] = useState(false);
   const [open, setOpen] = useState(false);
+  const [pathname, setPathname] = useState("/");
+
+  useEffect(() => {
+    setPathname(window.location.pathname);
+  }, []);
 
   // Supabase URL & Anon Key auslesen (für Browser-Client)
   const supabaseUrl = process.env.SUPABASE_URL || process.env.NEXT_PUBLIC_SUPABASE_URL;
@@ -186,7 +191,7 @@ export function NavbarClient({ user, role = "partner" }: NavbarClientProps) {
             </div>
           ) : (
             <Button asChild className="bg-primary hover:bg-primary/95 text-white dark:text-blue-500">
-              <Link href={`/auth/login?next=${typeof window !== 'undefined' ? window.location.pathname : '/'}`}>Anmelden</Link>
+              <Link href={`/auth/login?next=${pathname}`}>Anmelden</Link>
             </Button>
           )}
         </nav>
@@ -269,7 +274,7 @@ export function NavbarClient({ user, role = "partner" }: NavbarClientProps) {
             </Button>
           ) : (
             <Button asChild className="w-full bg-primary hover:bg-primary/95 text-white dark:text-blue-500" onClick={() => setIsMobileMenuOpen(false)}>
-              <Link href={`/auth/login?next=${typeof window !== 'undefined' ? window.location.pathname : '/'}`}>Anmelden</Link>
+              <Link href={`/auth/login?next=${pathname}`}>Anmelden</Link>
             </Button>
           )}
         </div>

shop/components/login-form.tsx

@@ -14,7 +14,7 @@ import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
 import Link from "next/link";
 import { useRouter } from "next/navigation";
-import { useState } from "react";
+import { useState, useEffect } from "react";
 
 export function LoginForm({
   className,
@@ -24,8 +24,13 @@ export function LoginForm({
   const [password, setPassword] = useState("");
   const [error, setError] = useState<string | null>(null);
   const [isLoading, setIsLoading] = useState(false);
+  const [messageParam, setMessageParam] = useState<string | null>(null);
   const router = useRouter();
 
+  useEffect(() => {
+    setMessageParam(new URLSearchParams(window.location.search).get('message'));
+  }, []);
+
   const handleLogin = async (e: React.FormEvent) => {
     e.preventDefault();
     setIsLoading(true);
@@ -35,6 +40,10 @@ export function LoginForm({
 
     try {
       const res = await signIn(email, password);
+      if (!res.success) {
+        setError(res.error || "An error occurred");
+        return;
+      }
       if (nextParam) {
         router.push(nextParam);
       } else if (res.role === "admin") {
@@ -90,17 +99,11 @@ export function LoginForm({
                   onChange={(e) => setPassword(e.target.value)}
                 />
               </div>
-            {(() => {
-              const messageParam = typeof window !== 'undefined' ? new URLSearchParams(window.location.search).get('message') : null;
-              if (messageParam === "concurrent") {
-                return (
-                  <p className="text-sm text-amber-500 bg-amber-500/10 border border-amber-500/20 p-3 rounded-lg text-center font-medium">
-                    Sie wurden abgemeldet, da Sie sich an einem anderen Gerät angemeldet haben.
-                  </p>
-                );
-              }
-              return null;
-            })()}
+            {messageParam === "concurrent" && (
+              <p className="text-sm text-amber-500 bg-amber-500/10 border border-amber-500/20 p-3 rounded-lg text-center font-medium">
+                Sie wurden abgemeldet, da Sie sich an einem anderen Gerät angemeldet haben.
+              </p>
+            )}
             {error && <p className="text-sm text-red-500">{error}</p>}
             <Button type="submit" className="w-full" disabled={isLoading}>
               {isLoading ? "Logging in..." : "Login"}

shop/lib/actions/auth.ts

@@ -1,38 +1,68 @@
 'use server'
 
 import { createClient } from '@/lib/supabase/server'
+import { createAdminClient } from '@/lib/supabase/admin'
 import { headers } from 'next/headers'
 
 export async function signIn(email: string, password: string) {
-  const supabase = await createClient()
-  const { data, error } = await supabase.auth.signInWithPassword({
-    email,
-    password,
-  })
-  if (error) {
-    throw new Error(error.message)
-  }
-
-  const userId = data.user?.id
-  if (userId) {
-    const { data: userData, error: userError } = await supabase
-      .from('users')
-      .select('role')
-      .eq('id', userId)
-      .single()
-
-    if (userError || !userData || (userData.role !== 'partner' && userData.role !== 'admin')) {
-      await supabase.auth.signOut()
-      throw new Error("Zugriff verweigert. Nur registrierte Partner dürfen sich anmelden.")
+  try {
+    const supabase = await createClient()
+    const { data, error } = await supabase.auth.signInWithPassword({
+      email,
+      password,
+    })
+    if (error) {
+      return { success: false, error: error.message }
     }
 
-    // Andere aktive Sitzungen beenden
-    await supabase.auth.signOut({ scope: 'others' })
+    const userId = data.user?.id
+    if (userId) {
+      let { data: userData, error: userError } = await supabase
+        .from('users')
+        .select('role')
+        .eq('id', userId)
+        .single()
 
-    return { success: true, role: userData.role }
+      if (userError || !userData) {
+        // Fallback: create database records if missing for this authenticated user
+        try {
+          const adminSupabase = createAdminClient()
+          
+          // Ensure profile exists
+          await adminSupabase.from('profiles').insert([{ id: userId }]).select()
+          
+          // Ensure user exists
+          const { data: insertedUser, error: insertError } = await adminSupabase
+            .from('users')
+            .insert([{ id: userId, role: 'partner' }])
+            .select('role')
+            .single()
+
+          if (!insertError && insertedUser) {
+            userData = insertedUser
+            userError = null
+          }
+        } catch (adminErr) {
+          console.error("Failed to backfill user records:", adminErr)
+        }
+      }
+
+      if (userError || !userData || (userData.role !== 'partner' && userData.role !== 'admin')) {
+        await supabase.auth.signOut()
+        return { success: false, error: "Zugriff verweigert. Nur registrierte Partner dürfen sich anmelden." }
+      }
+
+      // Andere aktive Sitzungen beenden
+      await supabase.auth.signOut({ scope: 'others' })
+
+      return { success: true, role: userData.role }
+    }
+
+    return { success: true, role: 'partner' }
+  } catch (err: any) {
+    console.error("SignIn error:", err)
+    return { success: false, error: err?.message || "Ein unerwarteter Fehler ist aufgetreten." }
   }
-
-  return { success: true, role: 'partner' }
 }
 
 export async function signUp(email: string, password: string) {