Add gzip compression middleware to API

[Antonod1988]

Summary

• add Express compression middleware before API routes
• add compression and TypeScript types to the API workspace
• cover gzip negotiation with a Supertest check against /api/openapi.json

Closes #70.

Tests

• npm --workspace api test -- --runTestsByPath src/tests/compression.test.ts --coverage=false --runInBand --forceExit
• npx eslint src/app.ts src/tests/compression.test.ts (passes with existing warning: app.ts has unused logger)

Note: npm --workspace api run typecheck currently fails on existing controller errors where next is referenced but not defined; this change does not touch those files.

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