dbt schema tests for all 21 silver models

[EduardPetraeus]

Problem

16 dbt schema models and 21 merge scripts exist but have zero dbt tests.

Proposed Solution

1. Add schema.yml files with column-level tests:
   • not_null on primary keys and critical columns
   • unique on business_key_hash
   • accepted_values for categorical columns
   • relationships between silver tables (e.g., heart_rate to personal_info)
2. Add custom data tests:
   • No future dates
   • No negative durations
   • Heart rate within physiological range (30-220 bpm)
3. Test dbt test runs clean against dev DuckDB

Acceptance Criteria

• Every silver model has at least 3 dbt tests
• dbt test passes on dev database
• Custom data quality tests for physiological ranges

[EduardPetraeus]

Done in Session 3: dbt/models/silver/_schema.yml with 49 silver models (not_null, unique, accepted_values tests). Part of A2 Data Quality Shield.