feat(deploy): prod compose split + host-memory monitoring (Stage 18)

Split the contour across the two prod hosts and retune for the small main host:

- Gate vpn+bot to the telegram-local profile. The CI test deploy now passes
  --profile telegram-local so the test contour still brings them; the prod main
  host omits both, and the prod bot runs standalone from docker-compose.bot.yml.
- docker-compose.prod.yml (main-host overlay): publish caddy 80/443 (no host
  caddy in prod; caddy owns ACME) and gateway 9443 (the remote bot dials in over
  mTLS); GOMAXPROCS=2, smaller memory caps and 7d Prometheus retention for the
  2 vCPU / 1.9 GiB host. It launches deliberately undersized; resize reactively.
- docker-compose.bot.yml: standalone bot for the tg host (no VPN, OTLP off since
  otelcol is unreachable from there, dials the main host's bot-link).
- Add node_exporter + a Prometheus scrape so host memory pressure (the OOM
  signal on the tight main host), not just per-container docker_stats, is visible.
- Soften AWG_CONF to a default: only the profiled vpn sidecar consumes it, and
  compose interpolates profiled-out services too, so prod must not require it.

deploy/docker-compose.bot.yml

@@ -0,0 +1,53 @@
+# Production Telegram bot host descriptor (standalone — NOT an overlay). Run only on
+# the bot host:
+#   docker compose -f docker-compose.bot.yml up -d
+#
+# The bot egresses to the Bot API directly (no VPN sidecar) and dials the main host's
+# published bot-link :9443 over mTLS. It exports no telemetry — otelcol lives on the
+# main host and is unreachable from here — so observe it via `docker logs` on this host.
+# Values come from the prod-deploy workflow (PROD_ secrets/variables); BOT_IMAGE is the
+# pushed registry tag and BOTLINK_GATEWAY_ADDR is the main host's <ip>:9443.
+name: scrabble-bot
+
+services:
+  bot:
+    container_name: scrabble-telegram-bot
+    image: ${BOT_IMAGE:?set BOT_IMAGE to the registry tag}
+    restart: unless-stopped
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
+    environment:
+      TELEGRAM_BOT_TOKEN: ${TELEGRAM_BOT_TOKEN:?set TELEGRAM_BOT_TOKEN}
+      TELEGRAM_GAME_CHANNEL_ID: ${TELEGRAM_GAME_CHANNEL_ID:-}
+      TELEGRAM_CHAT_ID: ${TELEGRAM_CHAT_ID:-}
+      TELEGRAM_PROMO_BOT_TOKEN: ${TELEGRAM_PROMO_BOT_TOKEN:-}
+      TELEGRAM_BOT_USERNAME: ${TELEGRAM_BOT_USERNAME:-}
+      TELEGRAM_BOT_LINK: ${TELEGRAM_BOT_LINK:-}
+      TELEGRAM_MINIAPP_URL: ${TELEGRAM_MINIAPP_URL:?set TELEGRAM_MINIAPP_URL}
+      # Real Bot API in prod (the test contour pins TELEGRAM_TEST_ENV=true instead).
+      TELEGRAM_TEST_ENV: "false"
+      TELEGRAM_API_BASE_URL: ${TELEGRAM_API_BASE_URL:-}
+      TELEGRAM_OWNS_UPDATES: "true"
+      # Dials the main host's published bot-link. ServerName stays `gateway` (the cert
+      # SAN), so TLS validation is independent of the dial address.
+      TELEGRAM_GATEWAY_ADDR: ${BOTLINK_GATEWAY_ADDR:?set BOTLINK_GATEWAY_ADDR (main:9443)}
+      TELEGRAM_BOTLINK_SERVER_NAME: gateway
+      TELEGRAM_BOTLINK_TLS_CERT: /certs/bot.crt
+      TELEGRAM_BOTLINK_TLS_KEY: /certs/bot.key
+      TELEGRAM_BOTLINK_TLS_CA: /certs/ca.crt
+      TELEGRAM_LOG_LEVEL: ${LOG_LEVEL:-info}
+      TELEGRAM_SERVICE_NAME: scrabble-telegram-bot
+      # No telemetry export: otelcol is on the main host, unreachable from here.
+      TELEGRAM_OTEL_TRACES_EXPORTER: none
+      TELEGRAM_OTEL_METRICS_EXPORTER: none
+      GOMAXPROCS: "1"
+    volumes:
+      - ${SCRABBLE_CONFIG_DIR:-.}/certs:/certs:ro
+    deploy:
+      resources:
+        limits:
+          cpus: "1.0"
+          memory: 256M