chore(migration): replace magic strings with EntityNames constants

[joshsmithxrm]

Summary

Replace hardcoded entity name strings with constants for better maintainability.

Problem

Throughout PPDS.Migration, magic strings are used for entity names:

• "isdefault"
• "account"
• "systemuser"
• "team"

This creates risk of typos and makes refactoring difficult.

Solution

1. Create EntityNames static class with constants
2. Replace magic strings with constant references
3. Consider using existing generated entity constants where available

Example

// Before
if (entityName == "systemuser")

// After
if (entityName == EntityNames.SystemUser)

Files to Modify

• Create: src/PPDS.Migration/Constants/EntityNames.cs
• Modify: Multiple files in src/PPDS.Migration/

Work Stream

Stream B - Code Patterns

Acceptance Criteria

• Constants class created
• Magic strings replaced
• All existing tests pass