feat(infra): add redis container as 24/7 queue + cache base (SP-1)

redis:7-alpine, 256MB maxmemory, AOF appendonly ON, allkeys-lru.
docker volume ${RUNTIME_PATH}/redis-data로 영속화.
Plan-B 후속 트랙(insta-render/music-render/video-render Windows
워커)의 BLPOP 큐 + NAS↔Windows pub/sub의 base.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -290,3 +290,18 @@ services:
       - ${RUNTIME_PATH}:/runtime:rw
       - ${RUNTIME_PATH}/scripts:/scripts:ro
       - /var/run/docker.sock:/var/run/docker.sock
+
+  redis:
+    image: redis:7-alpine
+    container_name: redis
+    restart: unless-stopped
+    ports:
+      - "6379:6379"
+    volumes:
+      - ${RUNTIME_PATH}/redis-data:/data
+    command: redis-server --appendonly yes --maxmemory 256mb --maxmemory-policy allkeys-lru
+    healthcheck:
+      test: ["CMD", "redis-cli", "ping"]
+      interval: 60s
+      timeout: 5s
+      retries: 3