feat(deploy): wire the SMTP relay through every contour

Add the backend confirm-code relay env to compose (BACKEND_SMTP_HOST/PORT/
USERNAME/PASSWORD/FROM + BACKEND_PUBLIC_BASE_URL), sourced from SMTP_RELAY_* /
SMTP_RELAY_FROM / PUBLIC_BASE_URL. An empty host keeps the backend on the log
mailer so a contour without relay credentials still boots. Port defaults to 465
(implicit TLS). Map the TEST_ set in ci.yaml and the PROD_ set in prod-deploy.yaml
(both the deploy-main env and the env.sh heredoc). Document the six variables in
.env.example and the deploy README (secrets: user/pass; variables: host/port/from
+ the per-contour PUBLIC_BASE_URL, required whenever the relay host is set).

deploy/.env.example

@@ -26,6 +26,21 @@ LOG_LEVEL=info
 # real contour value with `openssl rand -base64 32` (Gitea TEST_/PROD_EXPORT_SIGN_KEY).
 EXPORT_SIGN_KEY=dev-export-sign-key
 
+# --- Transactional email (Selectel relay) -----------------------------------
+# Confirm-code email via the shared Selectel relay (one relay for every contour;
+# limit 100 msgs / 5 min). Empty SMTP_RELAY_HOST makes the backend log codes instead
+# of sending (dev). Port 465 = implicit TLS, else STARTTLS; no client cert is needed.
+# FROM must use the prod domain (Selectel only accepts the verified sender domain), so
+# it is the same on every contour. PUBLIC_BASE_URL is the canonical https origin for
+# links in the email — the contour's own public URL. Gitea TEST_/PROD_SMTP_RELAY_* +
+# TEST_/PROD_PUBLIC_BASE_URL.
+SMTP_RELAY_HOST=
+SMTP_RELAY_PORT=465
+SMTP_RELAY_USER=                       # secret
+SMTP_RELAY_PASS=                       # secret
+SMTP_RELAY_FROM=no-reply@erudit-game.ru
+PUBLIC_BASE_URL=                       # required when SMTP_RELAY_HOST is set (e.g. https://erudit-game.ru)
+
 # --- Edge / caddy -----------------------------------------------------------
 # Test: ":80" (the host caddy terminates TLS and forwards to scrabble:80 on the
 # external `edge` network). Prod: a domain so caddy does its own ACME.

deploy/README.md

@@ -96,6 +96,12 @@ without it Docker's resolver handles `otelcol`, `gateway` and `api.telegram.org`
 | `VITE_TELEGRAM_GAME_CHANNEL_NAME` | variable | _(empty)_ | UI build-arg: the landing "Play in Telegram" link, the bot's game channel (e.g. `https://t.me/Erudit_Game`). |
 | `VITE_VK_APP_LINK` | variable | _(empty)_ | UI build-arg: the landing "Play on VK" link, the VK Mini App (full URL, `https://vk.com/app<id>`). |
 | `VITE_GATEWAY_URL` | variable | _(empty)_ | UI build-arg: gateway origin; empty = same-origin (the usual single-origin deploy). |
+| `SMTP_RELAY_HOST` | variable | _(empty)_ | Selectel SMTP relay host for confirm-code email. Empty leaves the backend on the log mailer (email disabled) — the contour still boots. One relay for every contour (limit 100 msgs / 5 min). |
+| `SMTP_RELAY_PORT` | variable | `465` | Relay port. `465` selects implicit TLS; any other port uses STARTTLS. No client certificate is needed (the server cert is validated against the system roots). |
+| `SMTP_RELAY_USER` | secret | _(empty)_ | Relay SMTP AUTH username. |
+| `SMTP_RELAY_PASS` | secret | _(empty)_ | Relay SMTP AUTH password. |
+| `SMTP_RELAY_FROM` | variable | `no-reply@localhost` | Sender address. **Must use the prod domain** (`no-reply@erudit-game.ru`) — Selectel only accepts the verified sender domain — so it is the same on every contour. |
+| `PUBLIC_BASE_URL` | variable | _(empty)_ | Canonical public https origin for links in the email (the contour's own URL, e.g. `https://erudit-game.ru`). **Required by the backend whenever `SMTP_RELAY_HOST` is set** — it is never derived from a request Host header (anti-injection). |
 
 The six `VITE_*` are **build-args** baked into the gateway and landing images at
 build time (both targets share one UI build stage — keep the args identical so it is
@@ -198,11 +204,13 @@ players arrive.
 **`PROD_` Gitea set** (mirrors `TEST_`, mapped onto the unprefixed names above) — secrets:
 `PROD_{POSTGRES_PASSWORD, GM_BASICAUTH_HASH, GRAFANA_ADMIN_PASSWORD, TELEGRAM_BOT_TOKEN,
 TELEGRAM_PROMO_BOT_TOKEN, EXPORT_SIGN_KEY, REGISTRY_PASSWORD, SSH_KEY, SSH_KNOWN_HOSTS, BOTLINK_CA,
-BOTLINK_GATEWAY_CERT, BOTLINK_GATEWAY_KEY, BOTLINK_BOT_CERT, BOTLINK_BOT_KEY}`; variables:
+BOTLINK_GATEWAY_CERT, BOTLINK_GATEWAY_KEY, BOTLINK_BOT_CERT, BOTLINK_BOT_KEY,
+SMTP_RELAY_USER, SMTP_RELAY_PASS}`; variables:
 `PROD_{REGISTRY_USER, MAIN_HOST, TG_HOST, CADDY_SITE_ADDRESS, GM_BASICAUTH_USER,
 GRAFANA_ROOT_URL, LOG_LEVEL, DICT_VERSION, TELEGRAM_MINIAPP_URL, TELEGRAM_GAME_CHANNEL_ID,
 TELEGRAM_CHAT_ID, TELEGRAM_BOT_USERNAME, VITE_TELEGRAM_BOT_ID, VITE_TELEGRAM_LINK,
-VITE_TELEGRAM_GAME_CHANNEL_NAME, VITE_VK_APP_LINK}`.
+VITE_TELEGRAM_GAME_CHANNEL_NAME, VITE_VK_APP_LINK,
+SMTP_RELAY_HOST, SMTP_RELAY_PORT, SMTP_RELAY_FROM, PUBLIC_BASE_URL}`.
 
 ## Host-side setup (outside this repo)
 

deploy/docker-compose.yml

@@ -136,6 +136,18 @@ services:
       # GOMAXPROCS matches the CPU limit below so the Go scheduler aligns with the
       # cgroup quota (the runtime otherwise sees all of the host's cores).
       GOMAXPROCS: "2"
+      # Transactional email (confirm-codes) via the shared Selectel relay. An empty
+      # host makes the backend log codes instead of sending them (dev default). Port
+      # 465 selects implicit TLS; any other port uses STARTTLS. The From uses the prod
+      # domain (Selectel only accepts the verified sender domain), so it is the same on
+      # every contour. PUBLIC_BASE_URL is the canonical origin for links in the email
+      # (never a request Host header) — required whenever the relay host is set.
+      BACKEND_SMTP_HOST: ${SMTP_RELAY_HOST:-}
+      BACKEND_SMTP_PORT: ${SMTP_RELAY_PORT:-465}
+      BACKEND_SMTP_USERNAME: ${SMTP_RELAY_USER:-}
+      BACKEND_SMTP_PASSWORD: ${SMTP_RELAY_PASS:-}
+      BACKEND_SMTP_FROM: ${SMTP_RELAY_FROM:-no-reply@localhost}
+      BACKEND_PUBLIC_BASE_URL: ${PUBLIC_BASE_URL:-}
     # The dictionary lives on a named volume seeded from the image on first boot
     # (the image's /opt/dawg is owned by the nonroot UID, which the fresh volume
     # inherits). The admin console writes new version subdirectories here, and the