fix(frontend): use nested schema required fields

[anthonychengit]

What changes were proposed in this PR?

Nested autofill properties now determine requiredness from the JSON Schema object that directly owns the property.

	Before	After
Required property in a $ref definition	Could receive an invalid empty option	Receives only propagated attribute names
Optional nested property sharing a root-level name	Could lose its empty option	Retains the empty option

DynamicSchemaService.mutateProperty supplies the owning schema to its match and mutation callbacks. WorkflowCompilingService uses that schema's required array when constructing autofill enums.

Any related issues, documentation, discussions?

Closes #7826.

How was this PR tested?

Added positive and negative regression coverage for required and optional nested properties, plus callback coverage for the owning schema.

cd frontend
node node_modules\@angular\cli\bin\ng.js test --watch=false --include src/app/workspace/service/dynamic-schema/dynamic-schema.service.spec.ts --include src/app/workspace/service/compile-workflow/workflow-compiling.service.spec.ts

Result: 2 test files passed; 62 tests passed.

cd frontend
node .yarn\releases\yarn-4.14.1.cjs run format:ci
git diff --check

Result: both commands completed successfully.

Was this PR authored or co-authored using generative AI tooling?

Generated-by: Codex was used for implementation and verification assistance. I reviewed the final code and test output before submission.

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Backport auto-label report

This fix: PR was checked against each actively-supported release branch. release/* labels drive the post-merge backport, so add or remove one to change where this fix lands.

Release branch	Analysis
✅ release/v1.2	Change detected on this branch — label added; this fix is queued to backport here. Requested review from @xuang7.

Auto-label run.

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Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @aglinxinyuan, @kunwp1
  You can notify them by mentioning @aglinxinyuan, @kunwp1 in a comment.