[User Story] Create ghost-compose template and static files

[noahwhite]

Story Summary

As a platform engineer, I want to create the ghost-compose template and static files in the OpenTofu module, so that the Docker Compose configuration can be deployed via Ignition at boot time.

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✅ Acceptance Criteria

• compose.yml.tftpl template created with env_file sourcing both .env.config and /var/mnt/storage/ghost-compose/.env.secrets
• env.config.tftpl template created with non-secret configuration variables
• caddy/Caddyfile static file created using {$VAR} syntax for runtime secret substitution
• caddy/snippets/ActivityPub static file created
• caddy/snippets/Logging static file created
• caddy/snippets/SecurityHeaders static file created
• caddy/snippets/TrafficAnalytics static file created
• mysql-init/create-databases.sh static file created with executable permissions
• All files placed under opentofu/modules/vultr/instance/userdata/ghost-compose/

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📝 Additional Context

• Design: Files should match upstream TryGhost/ghost-docker structure where applicable
• The Caddyfile must use {$HEALTH_CHECK_TOKEN} instead of hardcoded token values
• compose.yml must source two env files: local .env.config and remote .env.secrets

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📦 Definition of Ready

• Acceptance criteria defined
• No unresolved external dependencies
• Story is estimated
• Team has necessary skills and access
• Priority is clear
• Business value understood

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✅ Definition of Done

• All acceptance criteria met
• Peer-reviewed
• Files syntactically valid (compose.yml, Caddyfile)
• No secrets in any created files

[linear]

GHO-46