Fixes #95

Problem

Slow PostgreSQL queries (>1s) when fetching contract data due to 2MB rows with large BYTEA fields mixed with frequently queried metadata.

Solution

Split the contracts table into separate metadata and data tables to optimize query performance.

Changes

• Migration 0004: Creates contract_metadata and contract_data tables
• Index: Added idx_contract_metadata_state for faster state filtering
• Storage: Updated all PostgreSQL storage methods to use split tables
• Safety: Preserves existing data and includes rollback migration

Files Modified

• src/storage/postgres/migrations/0004_split_contract_tables.{up,down}.sql
• src/storage/sqlx.rs - Added new table structs
• src/storage/postgres/mod.rs - Updated storage implementation

Expected Performance

Query times should improve from >1s to <100ms by only loading metadata when contract data isn't needed.