chore: settle product naming across app, widget and deployments

One word everywhere: ReplyPier in UI copy, package and image names, the
replypier.site domains (app/api/docs/help), REPLYPIER_* settings and the
--rp-* design tokens.

- public widget API is window.ReplyPier with replypierId / replypierBaseUrl /
  replypierConfig / replypierToken, loader at webclient/replypier.min.js;
  both bundles rebuilt from source
- NOTICE, llms.txt, CONTRIBUTING, HELP_CENTER_INFRA and the demo runtime
  config rewritten; the demo config ships no third-party keys
- migration adds the ReplyPier managed model value to the AI model enum
- local compose project, database, role, volume and Docker network carry the
  same name

backend/tests/services/test_ticket_privacy.py

@@ -41,7 +41,7 @@ class TestScrubOutbound:
         assert scrub_outbound(text, (OWNER_EMAIL,)) == text
 
     def test_own_email_matched_case_insensitively(self):
-        text = "Your account Arun@replypier.site is fixed."
+        text = "Your account Arun@ReplyPier.Site is fixed."
         assert scrub_outbound(text, (OWNER_EMAIL,)) == text
 
     def test_own_phone_survives_reformatting(self):