[User Story] Update dev environment to pass Ghost config values

[noahwhite]

Story Summary

As a platform engineer, I want to update the dev environment main.tofu to pass Ghost configuration values to the instance module, so that the ephemeral config is properly populated for the dev environment.

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✅ Acceptance Criteria

• ghost_domain value passed to vm module (e.g., "separationofconcerns.dev")
• ghost_admin_domain value passed to vm module (e.g., "admin.separationofconcerns.dev")
• mail_smtp_user value passed to vm module
• admin_ip value passed to vm module (from existing Bitwarden secret)
• Optional variables use defaults from module

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📝 Additional Context

• Design: Values should come from existing variables.tofu or Bitwarden secrets where applicable
• The admin_ip already exists in Bitwarden for firewall rules
• Domain values are static for dev environment

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📦 Definition of Ready

• Acceptance criteria defined
• Module variables defined (blocked by story 4)
• 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
• OpenTofu syntax valid (tofu validate passes)
• Peer-reviewed
• tofu plan shows expected changes

[linear]

GHO-51