[User Story] Update ghost.bu for ephemeral config files

[noahwhite]

Story Summary

As a platform engineer, I want to update ghost.bu to include the ephemeral config files in the storage.files section, so that Ignition deploys the Ghost Compose configuration at boot time.

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✅ Acceptance Criteria

• storage.files section updated to include /etc/ghost-compose/compose.yml with base64-encoded content
• storage.files section updated to include /etc/ghost-compose/.env.config with base64-encoded content
• storage.files section updated to include /etc/ghost-compose/caddy/Caddyfile
• storage.files section updated to include all Caddy snippets under /etc/ghost-compose/caddy/snippets/
• storage.files section updated to include /etc/ghost-compose/mysql-init/create-databases.sh with mode 0755
• All config files use mode 0644 (except mysql-init script which needs 0755)
• Template variables properly referenced (e.g., ${compose_yml}, ${env_config}, etc.)

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📝 Additional Context

• Design: Follow existing pattern in ghost.bu for base64-encoded file content
• Files are written to /etc/ghost-compose/ (ephemeral) not /var/mnt/storage/ghost-compose/ (persistent)
• Butane transpiles to Ignition JSON which is applied on first boot only

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📦 Definition of Ready

• Acceptance criteria defined
• Template files created (blocked by story 1)
• 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
• Butane syntax valid (transpiles without errors)
• Peer-reviewed
• No secrets in ghost.bu or template variables

[linear]

GHO-47