Add multilingual support (DE default, EN under /en/)

css/frontend.css

@@ -462,7 +462,43 @@ li {
 .header-actions {
   display: flex;
   align-items: center;
-  gap: 0.75rem;
+  gap: 0.65rem;
+}
+
+.lang-switch {
+  display: inline-flex;
+  align-items: center;
+  background-color: var(--bg-alt);
+  border: 1px solid var(--border);
+  border-radius: var(--radius-full);
+  padding: 0.18rem;
+  gap: 0.15rem;
+  flex-shrink: 0;
+}
+
+.lang-link {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  padding: 0.3rem 0.55rem;
+  font-size: 0.78rem;
+  font-weight: 700;
+  color: var(--text-muted);
+  border-radius: var(--radius-full);
+  text-decoration: none;
+  line-height: 1;
+  transition: var(--transition);
+}
+
+.lang-link:hover {
+  color: var(--primary-dark);
+  text-decoration: none;
+}
+
+.lang-link.active {
+  background-color: var(--primary);
+  color: #ffffff;
+  box-shadow: 0 1px 4px rgba(11, 79, 108, 0.2);
 }
 
 .header-cta-btn {