feat: Implement applyJoinRef and applyJoinRefs

[chinhtrung]

Summary

• Add applyJoinRef extension method for single join reference operations
• Add applyJoinRefs extension methods for multiple join reference operations (2 and 3 references)
• Add comprehensive tests demonstrating usage of the new extension methods
• Improve ergonomics when working with multiple join references in a single operation

Changes

• API: New extension methods in TypeSafeCriteriaBuilder:
  • applyJoinRef(ref, lambda) - for single reference operations
  • applyJoinRefs(ref1, ref2, lambda) - for 2 reference operations
  • applyJoinRefs(ref1, ref2, ref3, lambda) - for 3 reference operations
• Tests: Added comprehensive test coverage demonstrating equivalence with existing applyFilter patterns

Benefits

• Reduces boilerplate when working with multiple join references
• Provides cleaner syntax for complex multi-table operations
• Maintains type safety while improving readability

Test plan

• New extension methods work correctly with existing join reference patterns
• Tests demonstrate equivalence between new methods and existing applyFilter approach
• All existing functionality continues to work unchanged
• Tests cover both 2 and 3 reference scenarios using real entity relationships

[luanpotter]

LGTM

[luanpotter]

cc @QuinnB73