Fix sheets row cell values to round-trip scalars

[sminot]

RowInsertValues, RowUpdateValues and SheetQueryResponse.rows carried a second level of additional_properties, so a scalar cell value could not be represented in either direction:

# rows: [["G65", 3]]
ValueError: dictionary update sequence element #0 has length 1; 2 is required
# values["icd_code"] = "G65"
AttributeError: 'str' object has no attribute 'to_dict'

That left get_sheet_data, query_sheet_data, query_namespace_data, insert_sheet_data and update_sheet_data working only while the sheet was empty. The cells are free-form JSON, matching the Map<String, Object> and List<List<Object>> the API serves, so these models now carry a single level of additional_properties like Sample.metadata. The models are the generator's own output for the three corrected schemas; the rest of the spec is untouched to keep this off a full sync.

CirroBio/Cirro-backend#854 fixes RowInsert and RowUpdate at the source. SheetQueryResponse.rows cannot be fixed there — the cell sits two levels down in List<List<Object>> and micronaut-openapi has no annotation that reaches it — so the next schema sync will reintroduce the nested model for rows until the DTO signature changes.

Associated https://github.com/CirroBio/Cirro-backend/pull/854

Fixes #29

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