Update Readme

[zedimytch]

Note

Low Risk
Documentation-only updates plus a new config.example.json template; no runtime or behavior changes.

Overview
Improves onboarding docs in README.md by adding a clearer project description, local run instructions, and notes on configuration, bearer-token auth, permissions, and rate limiting.

Adds config.example.json as a template for local PostgreSQL/HTTP/environment settings to copy into config.json.

^{Written by Cursor Bugbot for commit 60e84b4. This will update automatically on new commits. Configure here.}