Port the full data ingestion layer from Python to Rust:
- Typed API client with 10 endpoints, serde response types, and error handling
- Team/player/transaction sync with proper upsert semantics (preserves hand field)
- Batter and pitcher CSV importers with 40+ column mappings each
- Parse helpers for float/int/endurance with 21 unit tests
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
