Add Tailwind CSS toggle, Markdown/WASM modes, and npm import resolution

- Tailwind CSS: toolbar checkbox injects Play CDN into preview, persisted
  per-fiddle via new options JSON column
- Markdown mode: uses marked.js CDN, renders markdown to HTML preview with
  CSS tab for custom styling
- WASM mode: starter template with inline WebAssembly add function, supports
  top-level await via module detection
- npm imports: auto-detect bare import specifiers in module code and inject
  importmap pointing to esm.sh CDN
- Module auto-detection for html-css-js mode (import/export statements)
- DB migration adds options column, server passes through all API endpoints
- All features work across preview, export, and embed

public/js/editors.js

@@ -39,6 +39,15 @@ export const MODE_TABS = {
     { id: 'js', label: 'Svelte', lang: 'html' },
     { id: 'css', label: 'CSS', lang: 'css' },
   ],
+  'markdown': [
+    { id: 'js', label: 'Markdown', lang: 'markdown' },
+    { id: 'css', label: 'CSS', lang: 'css' },
+  ],
+  'wasm': [
+    { id: 'html', label: 'HTML', lang: 'html' },
+    { id: 'css', label: 'CSS', lang: 'css' },
+    { id: 'js', label: 'JavaScript', lang: 'javascript' },
+  ],
 };
 
 // Map mode names to js_type values stored in DB
@@ -49,6 +58,8 @@ export const MODE_TO_JS_TYPE = {
   'react-ts': 'tsx',
   'vue': 'vue',
   'svelte': 'svelte',
+  'markdown': 'markdown',
+  'wasm': 'wasm',
 };
 
 export const JS_TYPE_TO_MODE = Object.fromEntries(