core-ranks/docs

Ranks Docs

1. 01_Overview.md - architecture and pieces
2. 02_Configuration.md - config.json + env vars
3. 03_Commands.md - every command + permission nodes
4. 04_Schema.md - MySQL tables, built-in group seeding
5. 05_Provider_Integration.md - how we replace Hytale's permission provider
6. 06_Cross_Server_Caching.md - cache + invalidation flow
7. 07_Operations.md - ops scenarios, debugging