fix(sms): inside Docker, send the server's public IP as the relay host, not the container's

Messages went out locally but not from the server. The relay gateway
identifies the sending server by `host`, and the owner's ruling (D26)
is that this is the server's IP. With SMS_RELAY_HOST unset, the driver
sent the machine's first external IPv4. On the bare PHP server that was
the real IP; inside the API container it is the container's (172.x).
Reproduced: a container on this machine reports 172.17.0.3.

- relay.driver: when SMS_RELAY_HOST is unset and the machine address is
  private (RFC 1918, CGNAT, link-local), the public IPv4 is looked up
  once (ipify, ifconfig.me, icanhazip in turn) and cached. If every
  lookup fails, it falls back to the old value. SMS_RELAY_HOST still wins.
- SmsService logs the host it will send at boot, and warns when it is
  still private, so a wrong value is visible instead of silent.
- Removed a debug console.log that wrote every recipient's mobile to the
  server log.
- .env.example and SERVER-SETUP-CHECKLIST: SMS_RELAY_HOST = this
  server's public IP.

Tests: relay-host.spec (5). All 254 API tests pass.

اپ: پیامک کد ورود دوباره به‌درستی ارسال می‌شود.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/.env.example

@@ -31,7 +31,10 @@ SMS_PROVIDER=relay
 # relay — all optional; URL and secret have built-in defaults.
 SMS_RELAY_URL=
 SMS_RELAY_SECRET=
-# The "host" field; blank sends this machine's first external IPv4.
+# The "host" field: this server's public IP (owner ruling D26). Blank sends the
+# machine's first external IPv4 — and when that is a private address (inside
+# Docker it is the container's 172.x), the public IP is looked up once at boot.
+# Setting it explicitly on the server is the surest; the boot log shows the value.
 SMS_RELAY_HOST=
 # "kave" (default, Kavenegar) or "default" to let the gateway pick the line.
 SMS_RELAY_PLATFORM=