Add host welcome/reset emails, email field, and /host URL; v2.0.7

- Host accounts now have an optional email field
- Creating a host with an email sends a welcome email with the portal
  URL, username, and password via Resend
- Resetting a password also emails the new credentials if the host
  has an email on file; admin sees a confirmation either way
- Admin panel shows email column and confirmation messages
- Portal URL changed from /host-upload to /host

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "2.0.6",
+  "version": "2.0.7",
   "type": "module",
   "scripts": {
     "dev": "vite",