Initial commit: code playground with multi-framework support

Express + SQLite backend with Monaco editor frontend.
Supports HTML/CSS/JS, TypeScript, React (JSX/TSX), Vue SFC,
and Svelte with live preview, console output, save/fork/share.

Includes CSS preprocessors (SCSS, Less), framework-specific
compilation (Babel, TypeScript, Svelte compiler), and
CDN-loaded runtime libraries for preview rendering.

public/js/console-panel.js

@@ -0,0 +1,27 @@
+const output = () => document.getElementById('console-output');
+
+export function initConsole() {
+  window.addEventListener('message', (e) => {
+    if (!e.data || e.data.type !== 'console') return;
+    if (e.data.method === 'clear') {
+      clearConsole();
+      return;
+    }
+    appendLine(e.data.method, (e.data.args || []).join(' '));
+  });
+
+  document.getElementById('btn-clear-console').addEventListener('click', clearConsole);
+}
+
+function appendLine(method, text) {
+  const el = document.createElement('div');
+  el.className = `console-line console-${method}`;
+  el.textContent = text;
+  const out = output();
+  out.appendChild(el);
+  out.scrollTop = out.scrollHeight;
+}
+
+export function clearConsole() {
+  output().innerHTML = '';
+}