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

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"}