deploy: require redis auth (--requirepass) across all consumers

Redis without a password was the root cause of the security incident
(cron miner via unauthenticated replication RCE, see
.forcc/deploy/SESSION2-FINDINGS.md). Loopback binding alone doesn't
protect against a compromised container inside the same compose
network, so wire REDIS_PASSWORD as a required secret everywhere redis
is used: backend/worker/worker-transcriber(-gpu), redis-exporter,
livekit and egress (via rendered templates). docker compose now
refuses to start without it instead of silently running unauthenticated.

docs/deploy/scaling.md

@@ -69,7 +69,7 @@ services:
       - ../.env
     environment:
       DATABASE_URL: ${DATABASE_URL:-postgresql+asyncpg://vidconf:vidconf@postgres:5432/vidconf}
-      REDIS_URL: ${REDIS_URL:-redis://redis:6379/0}
+      REDIS_URL: redis://:${REDIS_PASSWORD:?REDIS_PASSWORD не задан в .env}@redis:6379/0
       PLUGINS_CONFIG_PATH: ${PLUGINS_CONFIG_PATH:-config/plugins.yaml}
       PYTHONPATH: /app
     volumes: