fix(deploy): Grafana SMTP reuses relay host + explicit GRAFANA_SMTP_PORT

Drop the separate GRAFANA_SMTP_HOST (it duplicated SMTP_RELAY_HOST): Grafana differs from
the backend only in needing the STARTTLS port, so GF_SMTP_HOST is composed from
SMTP_RELAY_HOST + GRAFANA_SMTP_PORT (an explicit per-contour var, no magic default), reusing
SMTP_RELAY_USER/PASS. Wired through ci/prod/.env.example/README.

deploy/.env.example

@@ -47,13 +47,13 @@ PUBLIC_BASE_URL=                       # required when SMTP_RELAY_HOST is set (e
 
 # Operator alerts (email). The backend emails the admin on new feedback / word complaints
 # (coalesced), and Grafana emails infra alerts. Distinct senders; recipients may be several
-# comma-separated addresses. Grafana speaks STARTTLS, so it needs the relay's STARTTLS
-# host:port (GRAFANA_SMTP_HOST) and reuses SMTP_RELAY_USER/PASS. All empty = alerts off.
+# comma-separated addresses. Grafana reuses SMTP_RELAY_HOST/USER/PASS but dials the STARTTLS
+# port (it can't do the backend's implicit TLS), GRAFANA_SMTP_PORT. All empty = off.
 SMTP_RELAY_ADMIN_FROM=                 # backend admin-alert From (e.g. alerts@erudit-game.ru)
 ADMIN_EMAIL=                           # backend admin-alert recipient(s), comma-separated
 SMTP_RELAY_SERVICE_FROM=               # Grafana alert From (e.g. grafana@erudit-game.ru)
 SERVICE_EMAIL=                         # Grafana alert recipient(s), comma-separated
-GRAFANA_SMTP_HOST=                     # relay host:STARTTLS-port for Grafana (e.g. smtp.mail.selcloud.ru:1126)
+GRAFANA_SMTP_PORT=                     # Grafana STARTTLS port on SMTP_RELAY_HOST (Selectel: 1126)
 GF_SMTP_ENABLED=false                  # set true to enable Grafana alert emails
 
 # --- Edge / caddy -----------------------------------------------------------