feat(redis): add Redis 8 Alpine compose file

- Add docker-compose.yaml with password authentication commented out by
  default (no password required)
- Add .env.example with REDIS_PASSWORD documented and commented out

compose/redis/.env.example

@@ -0,0 +1,9 @@
+# Redis (Alpine) — environment variables
+# Copy this file to .env and adjust values for your environment.
+
+# Password for client connections. By default Redis starts with no password
+# (any client can connect). To require authentication:
+#   1. Set REDIS_PASSWORD below
+#   2. Uncomment the "command" line in docker-compose.yaml
+# Clients authenticate with: AUTH <password>
+# REDIS_PASSWORD=redis

compose/redis/docker-compose.yaml

@@ -0,0 +1,30 @@
+# Docker Compose file for Redis (Alpine)
+#
+# Usage:
+#   docker compose up -d
+#
+# By default, Redis starts with no password — any client can connect.
+# To require a password, set REDIS_PASSWORD in your .env file and uncomment
+# the "command" line below. Clients must then authenticate with AUTH
+# <password>.
+#
+# Environment variables (see .env.example for details):
+#   REDIS_PASSWORD - Optional password for client connections
+
+services:
+  redis:
+    # For available image tags, see https://hub.docker.com/_/redis
+    image: redis:8-alpine
+    container_name: redis
+    # To enable password authentication, set REDIS_PASSWORD in your .env file
+    # and uncomment the following line:
+    # command: redis-server --requirepass ${REDIS_PASSWORD}
+    ports:
+      # Map host port 6379 to container port 6379 (Redis default).
+      - "6379:6379"
+    volumes:
+      # Persist data beyond container lifetime.
+      - redis_data:/data
+
+volumes:
+  redis_data: