Send app broadcasts as Resend Broadcasts; add selective import from Resend; v2.7.0

- Broadcast Email creates and sends a Resend Broadcast to the Resend segment (unsubscribe handling, reports, New Episode topic, scheduling, test send)
- Subscribers: import chosen Resend-only contacts into the app list

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "2.6.1",
+  "version": "2.7.0",
   "type": "module",
   "scripts": {
     "dev": "vite",