docs: document Twilio-only-scoped Cloudflare Tunnel variant

Adds the actual config used for Summit Dental Care, where the tunnel
points at nginx's port-80 Twilio-only block instead of the whole app,
so only /api/twilio/* is reachable from the internet.

README.md

@@ -502,6 +502,44 @@ sudo systemctl start cloudflared
 
 ---
 
+### Variant — Tunnel scoped to Twilio webhooks only
+
+The example above tunnels the whole app (`service: http://localhost:3000`) to the public
+subdomain. If the only reason you need public access is Twilio's webhooks (inbound SMS/voice —
+see [Twilio In-Browser Calling Setup](#twilio-in-browser-calling-setup-dial-pad) below), point
+the tunnel at nginx's port-80 block instead, which only forwards `/api/twilio/*` and returns
+`403` for everything else (see [nginx.conf](nginx.conf)) — the rest of the app stays unreachable
+from the internet even though the tunnel is live.
+
+Example actually used for Summit Dental Care's Twilio integration — paste this into
+`/etc/cloudflared/config.yml` (`sudo nano /etc/cloudflared/config.yml`, this is a YAML file, not
+the certbot `.ini` credentials file from the LAN HTTPS section above):
+
+```yaml
+tunnel: fc423bdb-eaae-4af5-bd6d-961a60b1e624
+credentials-file: /home/gg/.cloudflared/fc423bdb-eaae-4af5-bd6d-961a60b1e624.json
+
+ingress:
+  - hostname: summit.mydentalofficemanagement.com
+    service: http://localhost:80
+  - service: http_status:404
+```
+
+Then route DNS and install the service same as Steps 6–7 above:
+
+```bash
+cloudflared tunnel route dns summit-dental-twilio summit.mydentalofficemanagement.com
+sudo cloudflared service install
+sudo systemctl enable cloudflared
+sudo systemctl start cloudflared
+```
+
+Skip Steps 8–9 (Vite `allowedHosts` / backend CORS) for this variant — the public hostname never
+reaches the frontend or triggers a login/API CORS check, only the unauthenticated Twilio webhook
+routes.
+
+---
+
 ### Multi-office overview
 
 Each office runs its own `cloudflared` tunnel on its own PC. Ports never conflict because each PC is a separate machine.