Send sign-in mail as HTML so quoted-printable wrapping cannot break the verify URL.

Staging was delivering magic links that looked expired because the token query string was encoded and wrapped in plaintext MIME. Also read rate-limit retry from the API error body, mention spam in the success copy, and document SES relay DNS.

Co-authored-by: Cursor <cursoragent@cursor.com>

messages/en/create/community/communitySave.json

@@ -4,6 +4,6 @@
   "placeholder": "email@domain.com",
   "characterCountTemplate": "{current}/{max}",
   "magicLinkSuccessTitle": "Check your email to log in",
-  "magicLinkSuccessDescription": "Your account has been created. A login link has been emailed to you.",
+  "magicLinkSuccessDescription": "We emailed a sign-in link. Open it on this device to continue — check spam or promotions if you don't see it.",
   "magicLinkErrorTitle": "Could not send link"
 }