Align public README and repo map with the actual LIME org structure

[gustavobftorres]

Parent

LIME-Protocol/lime-onchain#3

What to build

Correct public documentation that describes the LIME repository structure and Getting Started flow so it matches the actual LIME-Protocol org and the new SDK repository.

Acceptance criteria

• References to the old lime-exchange org are replaced with LIME-Protocol
• Repo map includes lime-onchain, lime-sdk, lime-oracle, lime-backend, lime-frontend, and lime-docs with accurate roles
• Getting Started points developers to the right first repo based on their goal
• Docs no longer promise a structure that does not exist

Blocked by

None - can start immediately