Closes #519

Summary

• hash investor-lock principal scope and funder query components before storing them in cache keys
• normalize investor-lock list query params so equivalent requests share a key while tenant, pagination, invoice, and funder inputs still isolate responses
• add regression coverage for same-invoice cross-funder cache misses and repeated same-funder hits
• document the updated investor-lock cache key formats
• restore logger/metrics support needed for the cache middleware tests and CI changed-file lint

Tests

• npm test -- --silent src/middleware/cache.test.js
• npx eslint src/middleware/cache.js src/middleware/cache.test.js src/logger.js src/metrics.js
• npx jest --no-coverage --forceExit tests/escrow.derived.test.js
• node --check src/index.js