Add Block Lottos OpenAPI

[scosemicolon]

Summary

• Add the Block Lottos OpenAPI to the Backend Ethereum APIs section.
• The API exposes public Polygon/Base lottery, draw history, jackpot, ad size, and wallet-signed ticket transaction builder routes.

Verification

• Confirmed https://blocklottos.com/openapi.json returns HTTP 200.
• Parsed the live spec as OpenAPI 3.1.0 with 16 paths.
• Confirmed the spec includes lottery stats, jackpot, draw history, ad, and ticket transaction routes.
• Ran git diff --check.