fix(i18n): render locale switch as links

Use locale-prefixed <Link> elements for EN/DE so language switching works even when client-side hydration is broken.

Co-authored-by: dennis <dennis@konkol.net>

app/components/Header.tsx

@@ -6,14 +6,14 @@ import { Menu, X, Mail } from "lucide-react";
 import { SiGithub, SiLinkedin } from "react-icons/si";
 import Link from "next/link";
 import { useLocale, useTranslations } from "next-intl";
-import { usePathname, useRouter } from "next/navigation";
+import { usePathname, useSearchParams } from "next/navigation";
 
 const Header = () => {
   const [isOpen, setIsOpen] = useState(false);
   const [scrolled, setScrolled] = useState(false);
   const locale = useLocale();
   const pathname = usePathname();
-  const router = useRouter();
+  const searchParams = useSearchParams();
   const t = useTranslations("nav");
 
   const isHome = pathname === `/${locale}` || pathname === `/${locale}/`;
@@ -44,23 +44,11 @@ const Header = () => {
     { icon: Mail, href: "mailto:contact@dk0.dev", label: "Email" },
   ];
 
-  const switchLocale = (nextLocale: string) => {
-    try {
-      const pathWithoutLocale = pathname.replace(new RegExp(`^/${locale}`), "") || "";
-      const hash = typeof window !== "undefined" ? window.location.hash : "";
-      // Rely on middleware to persist NEXT_LOCALE cookie.
-      // Use a hard navigation for maximum reliability (also fixes cases where
-      // client-side router navigation can be prevented by runtime errors).
-      const target = `/${nextLocale}${pathWithoutLocale}${hash}`;
-      if (typeof window !== "undefined") {
-        window.location.assign(target);
-        return;
-      }
-      router.push(target);
-    } catch {
-      // ignore
-    }
-  };
+  const pathWithoutLocale = pathname.replace(new RegExp(`^/${locale}`), "") || "";
+  const qs = searchParams.toString();
+  const query = qs ? `?${qs}` : "";
+  const enHref = `/en${pathWithoutLocale}${query}`;
+  const deHref = `/de${pathWithoutLocale}${query}`;
 
   // Always render to prevent flash, but use opacity transition
 
@@ -144,9 +132,8 @@ const Header = () => {
 
             <div className="hidden md:flex items-center space-x-3">
               <div className="flex items-center bg-white/40 border border-white/50 rounded-full overflow-hidden shadow-sm">
-                <button
-                  type="button"
-                  onClick={() => switchLocale("en")}
+                <Link
+                  href={enHref}
                   className={`px-3 py-1.5 text-xs font-semibold transition-colors ${
                     locale === "en"
                       ? "bg-stone-900 text-stone-50"
@@ -155,10 +142,9 @@ const Header = () => {
                   aria-label="Switch language to English"
                 >
                   EN
-                </button>
-                <button
-                  type="button"
-                  onClick={() => switchLocale("de")}
+                </Link>
+                <Link
+                  href={deHref}
                   className={`px-3 py-1.5 text-xs font-semibold transition-colors ${
                     locale === "de"
                       ? "bg-stone-900 text-stone-50"
@@ -167,7 +153,7 @@ const Header = () => {
                   aria-label="Sprache auf Deutsch umstellen"
                 >
                   DE
-                </button>
+                </Link>
               </div>
               {socialLinks.map((social) => (
                 <motion.a

e2e/i18n.spec.ts

@@ -4,15 +4,15 @@ test.describe("i18n routing", () => {
   test("language switcher navigates between locales", async ({ page }) => {
     await page.goto("/en", { waitUntil: "domcontentloaded" });
 
-    // Buttons have aria-labels; click the DE switcher.
-    const deButton = page.getByRole("button", { name: "Sprache auf Deutsch umstellen" });
-    if (await deButton.count()) {
+    // Locale switchers are links (work even without hydration)
+    const deLink = page.getByRole("link", { name: "Sprache auf Deutsch umstellen" });
+    if (await deLink.count()) {
       // Verify an EN label is present before switching (nav.home)
       await expect(page.getByRole("link", { name: "Home" })).toBeVisible();
 
       await Promise.all([
         page.waitForURL(/\/de(\/|$)/, { timeout: 30000 }),
-        deButton.click(),
+        deLink.click(),
       ]);
 
       // Verify the nav label updates after switching