chore(brand): rename the product to ReplyPier

The upstream project name is gone from code, assets, docs and build
output: brand strings, domains (replypier.site and its app/api/docs/help
subdomains), env prefixes, image and network names, the widget's public
JS API (window.ReplyPier, replypierId/BaseUrl/Config/Token), CSS tokens
(--rp-*), file and directory names, and the WordPress plugin package.

- widget loader is now webclient/replypier.min.js; both bundles rebuilt
  from source (backend/assets/widget.{js,css}, frontend/public/webclient)
- NOTICE, llms.txt, CONTRIBUTING, HELP_CENTER_INFRA and config.dev.js
  rewritten rather than string-swapped; the demo config no longer ships
  the previous vendor's Firebase/Razorpay/Google keys
- new migration replypier_ai_model_001 adds REPLYPIER to the managed
  AIModelType and rewrites pre-rename rows
- local compose project, database, role and volume renamed; LOCAL_DEPLOY
  documents carrying the old local data over

.claude/skills/write-e2e-test/SKILL.md

@@ -1,9 +1,9 @@
 ---
 name: write-e2e-test
-description: Write or change a ChatterMate Playwright end-to-end test (e2e/). Use when adding e2e coverage for a feature, fixing a failing e2e spec, or adding a page object, fixture or fake-LLM script.
+description: Write or change a ReplyPier Playwright end-to-end test (e2e/). Use when adding e2e coverage for a feature, fixing a failing e2e spec, or adding a page object, fixture or fake-LLM script.
 ---
 
-# Writing a ChatterMate e2e test
+# Writing a ReplyPier e2e test
 
 The suite lives in `e2e/`. Read `e2e/AUTHORING.md` first — it is the source of truth for
 layout and rules. The essentials: