Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

demos/cloudflare/README.md

@@ -0,0 +1,63 @@
+# EmDash Cloudflare Demo
+
+This demo shows EmDash running on Cloudflare Workers with D1 database.
+
+Uses Astro 6 + `@astrojs/cloudflare` v13 which runs the real `workerd` runtime in development.
+
+## Setup
+
+1. Create a D1 database:
+
+```bash
+pnpm db:create
+```
+
+2. Copy the database ID from the output and update `wrangler.jsonc`:
+
+```jsonc
+"d1_databases": [
+  {
+    "binding": "DB",
+    "database_name": "emdash-demo",
+    "database_id": "YOUR_DATABASE_ID_HERE"
+  }
+]
+```
+
+3. Start the dev server:
+
+```bash
+pnpm dev
+```
+
+EmDash runs migrations automatically on first request — no manual migration step needed.
+
+4. Open http://localhost:4321/\_emdash/admin
+
+## Preview
+
+After building, you can preview with the real Workers runtime:
+
+```bash
+pnpm build
+pnpm preview
+```
+
+## Deployment
+
+```bash
+pnpm deploy
+```
+
+This builds and deploys to Cloudflare Workers. EmDash handles migrations automatically on startup.
+
+## Notes
+
+- `astro dev` now uses `workerd` (the real Workers runtime) - development matches production
+- `wrangler types` runs automatically before dev/build to generate TypeScript types for bindings
+- No `platformProxy` config needed - Astro 6 handles this automatically
+
+## TODO
+
+- [ ] R2 storage for media uploads
+- [ ] Auth integration (Cloudflare Access or custom)