feat(i18n): responsive locale-switcher with SVG flags (closes #75)

public/css/haus-schleusingen.css

@@ -1316,3 +1316,122 @@ footer {
     text-align: center;
   }
 }
+
+/* LOCALE SWITCHER (sub-Issue D) */
+.locale-switcher {
+  display: flex;
+  align-items: center;
+  gap: 0.25rem;
+  list-style: none;
+  margin: 0;
+  padding: 0;
+}
+
+.locale-switcher__item {
+  display: flex;
+}
+
+.locale-switcher__option {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.4rem;
+  min-height: 44px;
+  min-width: 44px;
+  padding: 0.45rem 0.55rem;
+  border: 1px solid transparent;
+  border-radius: 4px;
+  text-decoration: none;
+  font-size: 0.78rem;
+  font-weight: 500;
+  letter-spacing: 0.04em;
+  color: rgb(255 255 255 / 90%);
+  background: transparent;
+  transition:
+    background 0.2s,
+    border-color 0.2s,
+    color 0.2s,
+    transform 0.15s;
+  cursor: pointer;
+}
+
+.locale-switcher__option:hover,
+.locale-switcher__option:focus-visible {
+  background: rgb(255 255 255 / 14%);
+  border-color: rgb(255 255 255 / 30%);
+  color: var(--white);
+  transform: translateY(-1px);
+}
+
+.locale-switcher__option.is-current {
+  background: rgb(255 255 255 / 20%);
+  border-color: var(--accent-light);
+  color: var(--white);
+  cursor: default;
+}
+
+.locale-switcher__option.is-current:hover {
+  transform: none;
+}
+
+nav.scrolled .locale-switcher__option {
+  color: var(--stone);
+}
+
+nav.scrolled .locale-switcher__option:hover,
+nav.scrolled .locale-switcher__option:focus-visible {
+  background: var(--warm);
+  border-color: var(--stone);
+  color: var(--dark);
+}
+
+nav.scrolled .locale-switcher__option.is-current {
+  background: var(--cream);
+  border-color: var(--accent);
+  color: var(--dark);
+}
+
+.locale-switcher__option .flag {
+  width: 24px;
+  height: 16px;
+  flex: 0 0 24px;
+  border-radius: 2px;
+  box-shadow: 0 0 0 1px rgb(0 0 0 / 15%);
+  display: block;
+}
+
+.locale-switcher__label {
+  white-space: nowrap;
+}
+
+/* Hide labels on small screens, keep the 44px flag target */
+@media (width <= 720px) {
+  .locale-switcher__label {
+    position: absolute;
+    width: 1px;
+    height: 1px;
+    padding: 0;
+    margin: -1px;
+    overflow: hidden;
+    clip: rect(0, 0, 0, 0);
+    white-space: nowrap;
+    border: 0;
+  }
+
+  .locale-switcher__option {
+    min-width: 44px;
+    padding: 0.55rem;
+  }
+}
+
+/* VISUALLY HIDDEN (a11y) */
+.visually-hidden {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  padding: 0;
+  margin: -1px;
+  overflow: hidden;
+  clip: rect(0, 0, 0, 0);
+  white-space: nowrap;
+  border: 0;
+}