[Agent][Analytics/dbt] Maintain DuckDB marts and quality contracts

[karnaksp]

Objective

Maintain typed bronze/silver/gold models that turn Yandex Music metadata into useful self-analytics.

Acceptance

• make dbt-build passes with the local DuckDB target.
• make doctor validates manifest/source alignment.
• Relationship, uniqueness, null, checksum, and stale-ingestion checks stay green.
• Lineage docs cover new marts and diagnostics.