Switch feedback reverse proxy from IIS to NGINX

- Add nginx-wp-suite.conf: static site + /api/feedback proxy to the Power
  Automate trigger (SNI on, Host header, POST-only, body cap)
- Remove IIS web.config
- Update feedback-config.js comment and DEPLOYMENT.md to the NGINX setup

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

feedback-config.js

@@ -16,11 +16,11 @@
    Leave it as an empty string to stay fully local (export/import only).
    See DEPLOYMENT.md for setup details and sample receivers.
 
-   This is set to the same-origin path '/api/feedback', which the IIS reverse
-   proxy (see web.config) forwards to the Power Automate HTTP trigger. Keeping it
-   relative means no CORS and the secret trigger URL never appears in client
-   code. Locally (no proxy) the POST simply fails silently and feedback is still
-   saved/exported from the browser.
+   This is set to the same-origin path '/api/feedback', which the NGINX reverse
+   proxy (see nginx-wp-suite.conf) forwards to the Power Automate HTTP trigger.
+   Keeping it relative means no CORS and the secret trigger URL never appears in
+   client code. Locally (no proxy) the POST simply fails silently and feedback is
+   still saved/exported from the browser.
    ────────────────────────────────────────────────────────────────────────── */
 window.FEEDBACK_ENDPOINT = '/api/feedback';