Exchange Integration: Manifold Markets

[realfishsam]

Implement support for Manifold Markets.

Manifold is mentioned in the README with its logo but currently lacks an implementation class in src/exchanges.

Tasks:

• Create ManifoldExchange class extending PredictionMarketExchange.
• Implement fetchMarkets using Manifold's public API.
• Implement searchMarkets.
• Map outcomes and data to UnifiedMarket format.

[femtotrader]

https://github.com/manifoldmarkets/manifold/blob/main/common/src/api/schema.ts could help