Add Redis to lgtm-podman-stack skill templates

[patterncatalyst]

Summary

Add Redis 7 (Alpine) as an optional service to the podman compose templates in ~/.claude/skills/lgtm-podman-stack/.

Tasks

• Add Redis service block to compose-full.yaml
• Create compose-with-redis.yaml template (app + Redis + LGTM)
• Verify Redis healthcheck in snippets/healthcheck-patterns.md
• Update references/ports-and-endpoints.md with Redis port 6379
• Update SKILL.md decision tree to include Redis variants

Needed by

• Example 16 (WebSockets — Redis pub/sub backplane)
• Example 25 (Caching Patterns — Redis as cache layer)