Add Marine Fuels endpoints

[karlwaldman]

Overview

Add support for marine fuel (bunker) pricing data.

Endpoints to Add

• GET /v1/marine-fuels - Get marine fuel prices
• GET /v1/marine-fuels/historical - Get historical marine fuel prices
• GET /v1/marine-fuels/latest - Get latest marine fuel prices

Types Needed

• MarineFuelsResponse
• MarineFuelsHistoricalOptions

Priority

P2 - Medium Value - Niche but valuable for maritime industry

Swagger Reference

See swagger/v1/swagger.json in oilpriceapi-api repo for schema details