Add shared ConceptFilter for CDM concept-table queries

[nicoloesch]

Summary

Adds ConceptFilter (omop_alchemy.cdm.query.ConceptFilter), a shared, reusable way to filter CDM concept-table queries by domain, vocabulary, concept ID, and standard/active status, with an optional row-count limit.

• Closes feat: centralised concept query filtering API #11.

Both omop-emb and omop-graph currently reimplement this same filtering logic independently against their own copies of the Concept model's column names. This gives both a single, shared implementation to depend on instead. Building it here rather than in either downstream package because omop_alchemy is the one place that owns the Concept model directly, so the filter can reference real columns (Concept.domain_id, Concept.standard_concept, etc.) rather than duck-typing against an opaquely-imported table.

Checklist

• Applied exactly one label (breaking, feature, fix, dependencies, or chore) — feature
• Tests pass locally (uv run pytest -q)
• Lint passes (uv run ruff check .)