Fix patternProperties validation to apply to all properties

[lahma]

Summary

• patternProperties validation was only applied to additional properties (not in the schema's properties collection), but the JSON Schema spec requires it to be evaluated against all object properties
• Changed ValidatePatternProperties to receive all properties for validation, while still correctly removing matched properties from the additional properties list for additionalProperties evaluation

Test plan

• 4 new tests added to PatternPropertyValidationTests.cs:
  • Defined property value doesn't match pattern → validation fails
  • Defined property value matches pattern → validation succeeds
  • Mixed defined + additional properties with pattern → works correctly
  • Defined property name doesn't match pattern regex → pattern not applied
• All 3 existing pattern property tests still pass
• All 452 tests pass with no regressions

Fixes #1736

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