Add Docker Compose setup

theme.js

@@ -0,0 +1,26 @@
+(function () {
+  const KEY = "frenchJourney.theme";
+  const root = document.documentElement;
+
+  function apply(theme) {
+    root.dataset.theme = theme;
+    localStorage.setItem(KEY, theme);
+    const button = document.querySelector("[data-theme-toggle]");
+    if (button) {
+      const dark = theme === "dark";
+      button.textContent = dark ? "Light" : "Dark";
+      button.setAttribute("aria-pressed", String(dark));
+    }
+  }
+
+  const saved = localStorage.getItem(KEY);
+  const preferred = window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
+  apply(saved || preferred);
+
+  window.addEventListener("DOMContentLoaded", () => {
+    const button = document.querySelector("[data-theme-toggle]");
+    if (!button) return;
+    button.onclick = () => apply(root.dataset.theme === "dark" ? "light" : "dark");
+    apply(root.dataset.theme || "light");
+  });
+})();