[fix] client/simple: insecure ctx clipboard copy

Uses the deprecated [`execCommand()`](https://developer.mozilla.org/en-US/docs/Web/API/Document/execCommand)
to copy content to clipboard if accessing the instance through HTTP, this method
isn't going away soon.

Closes https://github.com/searxng/searxng/issues/5359

client/simple/src/js/main/keyboard.ts

@@ -407,12 +407,31 @@ const toggleHelp = (keyBindings: typeof baseKeyBinding): void => {
 };
 
 const copyURLToClipboard = async (): Promise<void> => {
-  const currentUrlElement = document.querySelector<HTMLAnchorElement>(".result[data-vim-selected] h3 a");
-  assertElement(currentUrlElement);
+  const selectedResult = document.querySelector<HTMLElement>(".result[data-vim-selected]");
+  if (!selectedResult) return;
 
-  const url = currentUrlElement.getAttribute("href");
+  const resultAnchor = selectedResult.querySelector<HTMLAnchorElement>("a");
+  assertElement(resultAnchor);
+
+  const url = resultAnchor.getAttribute("href");
   if (url) {
-    await navigator.clipboard.writeText(url);
+    if (window.isSecureContext) {
+      await navigator.clipboard.writeText(url);
+    } else {
+      const selection = window.getSelection();
+      if (selection) {
+        const node = document.createElement("span");
+        node.textContent = url;
+        resultAnchor.appendChild(node);
+
+        const range = document.createRange();
+        range.selectNodeContents(node);
+        selection.removeAllRanges();
+        selection.addRange(range);
+        document.execCommand("copy");
+        node.remove();
+      }
+    }
   }
 };