docs: verify EverCore quickstart path

[hylarucoder]

Summary

• update the EverCore README basic usage snippet to use the actual POST JSON API contract
• add an explicit Python/Docker prerequisite note in Quick Start
• ignore local docker-compose override files used for machine-specific Docker fixes

Verification

• extracted and ran the README Basic Usage Python block locally against EverCore API
• confirmed POST /api/v1/memories and POST /api/v1/memories/search returned HTTP 200
• ran git diff --check