Split vendor_compliance_routes.py (1107 LOC) into thin route handlers
plus three service modules: VendorService (vendors CRUD/stats/status),
ContractService (contracts CRUD), and FindingService + ControlInstanceService
+ ControlsLibraryService (findings, control instances, controls library).
All files under 500 lines. 215 tests pass.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>