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

deploy/server/updater/deployment.py

@@ -100,12 +100,12 @@ class Deployment:
             if len(styles) != 1:
                 raise RuntimeError('网站组件的样式构建结果不完整。')
             shutil.copy2(styles[0], stage / 'assets/widget.css')
-        loader = stage / 'dashboard/webclient/chattermate.min.js'
+        loader = stage / 'dashboard/webclient/replypier.min.js'
         loader.parent.mkdir(exist_ok=True)
-        self.run([str(front / 'node_modules/.bin/esbuild'), 'src/webclient/chattermate.js',
+        self.run([str(front / 'node_modules/.bin/esbuild'), 'src/webclient/replypier.js',
                   '--bundle', '--minify', '--format=iife', '--target=es2015', '--loader:.svg=text',
                   '--define:process.env.NODE_ENV="production"',
-                  '--define:__CHATTERMATE_API_URL__=' + json.dumps(self.cfg['public_url'] + '/api/v1'),
+                  '--define:__REPLYPIER_API_URL__=' + json.dumps(self.cfg['public_url'] + '/api/v1'),
                   '--outfile=' + str(loader)], cwd=front)
         # Runtime configuration belongs to this installation, not to the repository.
         live_web = self.root / 'deploy/local/.state/dashboard'