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.

db.js

@@ -0,0 +1,43 @@
+import Database from 'better-sqlite3';
+import { mkdirSync } from 'fs';
+
+mkdirSync('data', { recursive: true });
+
+const db = new Database('data/fiddles.db');
+db.pragma('journal_mode = WAL');
+db.pragma('foreign_keys = ON');
+
+db.exec(`
+  CREATE TABLE IF NOT EXISTS fiddles (
+    id TEXT PRIMARY KEY,
+    title TEXT NOT NULL DEFAULT 'Untitled',
+    html TEXT NOT NULL DEFAULT '',
+    css TEXT NOT NULL DEFAULT '',
+    css_type TEXT NOT NULL DEFAULT 'css',
+    js TEXT NOT NULL DEFAULT '',
+    js_type TEXT NOT NULL DEFAULT 'javascript',
+    created_at TEXT NOT NULL DEFAULT (datetime('now')),
+    updated_at TEXT NOT NULL DEFAULT (datetime('now'))
+  )
+`);
+
+// Migration: add js_type column for existing databases
+try {
+  db.exec(`ALTER TABLE fiddles ADD COLUMN js_type TEXT NOT NULL DEFAULT 'javascript'`);
+} catch (_) { /* column already exists */ }
+
+export const stmts = {
+  insert: db.prepare(`
+    INSERT INTO fiddles (id, title, html, css, css_type, js, js_type)
+    VALUES (@id, @title, @html, @css, @css_type, @js, @js_type)
+  `),
+  get: db.prepare('SELECT * FROM fiddles WHERE id = ?'),
+  update: db.prepare(`
+    UPDATE fiddles SET title = @title, html = @html, css = @css,
+      css_type = @css_type, js = @js, js_type = @js_type, updated_at = datetime('now')
+    WHERE id = @id
+  `),
+  list: db.prepare('SELECT id, title, css_type, js_type, created_at, updated_at FROM fiddles ORDER BY updated_at DESC LIMIT 50'),
+};
+
+export default db;