Refactor ItemWin.w to use Business Entity pattern

[YorickKuindersma]

Summary

Refactors ItemWin.w to replace legacy fat-client direct database access with the Business Entity architecture pattern as documented in doc/business-entity-pattern.md.

Changes

New Files

• src/business/ItemDataset.i — Temp-table and dataset definition for the Item entity (ttItem, dsItem) with BEFORE-TABLE for change tracking
• src/business/ItemEntity.cls — Business Entity class inheriting OpenEdge.BusinessLogic.BusinessEntity with:
  • GetItemByNumber() — Read operation using ReadData()
  • UpdateItem() — Update operation using UpdateData()
  • ValidateItem() — Validation logic (price != 0, total on-hand value <= 6000)

Modified Files

• src/business/EntityFactory.cls — Added ItemEntity singleton management (GetItemEntity() method, cleanup in ResetInstances())
• src/ItemWin.w — Refactored to:
  • Remove direct database FIND statements
  • Add USING statements for business entity classes
  • Include ItemDataset.i for dataset definitions
  • Use EntityFactory and ItemEntity for all data operations
  • Delegate validation to ItemEntity:ValidateItem()
  • Use TRACKING-CHANGES for update operations
  • Remove legacy database query definitions

What was removed from ItemWin.w

• Direct FIND FIRST Item ... NO-LOCK / EXCLUSIVE-LOCK database access
• Inline validation logic (moved to ItemEntity:ValidateItem())
• Database query preprocessor definitions (INTERNAL-TABLES, QUERY-STRING, OPEN-QUERY)
• Connected Databases reference

Resolves #1