feat: add schema tests for core clinical models

[Hitendrasinhdata7]

What this PR does

Adds schema.yml with data quality tests for core clinical models
that were previously untested.

Models covered

• core__patient: not_null, unique, accepted_values for sex/death_flag
• core__encounter: not_null, unique, accepted_values for encounter_type
• core__condition: not_null, unique, accepted_values for condition_type
• core__procedure: not_null, unique, accepted_values for procedure_type
• core__medication: not_null, unique on primary key
• core__lab_result: not_null, unique on primary key
• core__observation: not_null, unique on primary key
• core__immunization: not_null, unique on primary key
• core__appointment: not_null, unique on primary key

Why

These models had no schema tests. Adding tests ensures
data quality and catches regressions early.

Related

Follows the same pattern as PR #1301

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[KetanP1618]

Looks good. Adding schema tests for core models improves data quality and helps catch issues early. Follows the same pattern as previous PRs and makes the models more reliable.

[amartinson193]

A YAML file for core models already exists here: https://github.com/tuva-health/tuva/blob/main/models/core/core_models.yml#L2136

Either update this PR to add additional tests to that file or close this PR please.