Define domain module boundaries for RIMS core vs domain-specific logic

[fusion94]

Description

RIMS should own structural, reusable platform capabilities. Domain applications should own regulations, terminology, specialized validations, and domain workflows.

This issue defines the boundary between the framework core and app-specific modules so that future work does not push firearms, wine, or other niche logic into shared infrastructure.

This should include concrete examples using armory-core and cellar-sync.

Acceptance Criteria

• Define what belongs in RIMS core
• Define what belongs in domain modules
• Document examples for armory-core domain logic
• Document examples for cellar-sync domain logic
• Add a simple decision rule for evaluating whether a feature belongs in core or domain
• Link or align the result with the RIMS boundary ADR