Split setup read models for MWP stabilization

[sigilabcodex]

This PR continues SKOSS architecture stabilization toward a usable MWP.

Highlights:

• Splits the broad setup read model into section-oriented helpers:
  • identity
  • customer
  • module
  • business
  • procurement
  • catalog
• Keeps getSetupWorkspace() as a compatibility wrapper
• Refactors the admin setup page to use clearer section-owned models
• Documents the near-term MWP stabilization path
• Preserves current setup behavior and URLs

Checks:

• npm run typecheck passed
• npm run build passed

This is not a procurement/inventory feature PR. It is a structural step to make the admin/setup foundation easier to evolve safely.