Add Statcast metrics ingestion from Baseball Savant

[grovecj]

Summary

The MLB Stats API provides sabermetric stats (WAR, wOBA, wRC+, FIP, xFIP) and expected statistics (xBA, xSLG, xwOBA), but does not include Statcast-specific metrics. These need to be sourced from Baseball Savant.

Missing Metrics

Batting

• Exit Velocity (avg)
• Launch Angle (avg)
• Barrel %
• Hard Hit %
• Sprint Speed
• Sweet Spot %

Pitching

• Exit Velocity Against (avg)
• Spin Rate (avg by pitch type)
• Extension
• Vertical/Horizontal Movement

Current State

• Schema already has columns for these metrics in PlayerBattingStats and PlayerPitchingStats
• Columns exist but are not populated
• MLB Stats API tracking and metricAverages endpoints return empty/error responses

Proposed Solution

Investigate Baseball Savant data sources:

1. CSV Downloads: https://baseballsavant.mlb.com/leaderboard/custom provides downloadable CSVs
2. Statcast Search API: May have endpoints for individual player data
3. Third-party libraries: Some wrapper libraries may provide access

Acceptance Criteria

• Identify reliable data source for Statcast metrics
• Create ingestion service for Statcast data
• Populate existing schema columns with real data
• Add tests for new ingestion logic

Related

• Depends on: Advanced stats ingestion from MLB API (in progress)
• Schema: PlayerBattingStats, PlayerPitchingStats advanced columns