feat: add random message selection and theme toggle

script.js picks a random entry from MESSAGES on load and on each "Check
again" click, and persists the chosen colour scheme in localStorage.
messages.js holds the MESSAGES array as a placeholder template to be
filled in with content.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

script.js

@@ -0,0 +1,59 @@
+/* Why is the DLR shut today?
+ * Picks a random message on load and on demand, and handles the
+ * colour-scheme toggle. Messages live in messages.js (MESSAGES). */
+
+(function () {
+  "use strict";
+
+  const FALLBACK = "Add some reasons in messages.js";
+  const messageEl = document.getElementById("message");
+  const refreshButton = document.getElementById("refresh");
+  const themeButtons = document.querySelectorAll("[data-set-theme]");
+  const THEME_KEY = "dlr-theme";
+
+  function pickMessage() {
+    if (!Array.isArray(MESSAGES) || MESSAGES.length === 0) {
+      return FALLBACK;
+    }
+    const index = Math.floor(Math.random() * MESSAGES.length);
+    return MESSAGES[index];
+  }
+
+  function showMessage() {
+    messageEl.textContent = pickMessage();
+  }
+
+  function applyTheme(theme) {
+    document.body.setAttribute("data-theme", theme);
+    themeButtons.forEach(function (button) {
+      const isActive = button.dataset.setTheme === theme;
+      button.setAttribute("aria-pressed", String(isActive));
+    });
+    try {
+      localStorage.setItem(THEME_KEY, theme);
+    } catch (err) {
+      /* localStorage unavailable; theme simply won't persist. */
+    }
+  }
+
+  function initTheme() {
+    let saved = null;
+    try {
+      saved = localStorage.getItem(THEME_KEY);
+    } catch (err) {
+      /* ignore */
+    }
+    applyTheme(saved === "original" ? "original" : "modern");
+  }
+
+  themeButtons.forEach(function (button) {
+    button.addEventListener("click", function () {
+      applyTheme(button.dataset.setTheme);
+    });
+  });
+
+  refreshButton.addEventListener("click", showMessage);
+
+  initTheme();
+  showMessage();
+})();