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_sql_guardrails.py

@@ -359,7 +359,7 @@ class TestRowScopeCaseInsensitivity:
         )
 
     def test_predicate_folds_both_sides(self):
-        result = self._ci("Arun@replypier.site")
+        result = self._ci("Arun@ReplyPier.Site")
         assert result.ok
         assert "LOWER(customer_email) = '%s'" % OWNER in result.sql
 
@@ -369,10 +369,10 @@ class TestRowScopeCaseInsensitivity:
         assert "'x'' or ''1''=''1'" in result.sql.lower()
 
     def test_exact_match_when_disabled(self):
-        result = scoped("SELECT id FROM orders", value="Arun@replypier.site")
+        result = scoped("SELECT id FROM orders", value="Arun@ReplyPier.Site")
         assert result.ok
         assert "LOWER(" not in result.sql
-        assert "customer_email = 'Arun@replypier.site'" in result.sql
+        assert "customer_email = 'Arun@ReplyPier.Site'" in result.sql
 
     def test_still_fails_closed(self):
         result = self._ci(value=None)