SCRUM-5881 add variants as attributes on allele document

[cmpich]

No description provided.

[claude]

Code Review: Changes look correct.

This PR cleanly adds variantHgvs as a searchable attribute on allele documents, with consistent changes across all four layers:

• Model (AlleleSearchResultDocument): new Set<String> field
• ES Mapping: text + keyword — consistent with similar fields like variantType
• Converter: properly null-checks location.getHgvs() before adding, and only sets the field when non-empty
• SearchHelper: registers both variantHgvs and variantHgvs.keyword for search

No issues found. LGTM.

[oblodgett]

These should be added to the variantSynonyms field and not add an extra field.