[feat] Support direct contract reads for the Avalon sUSDa price requests as a fallback from the Avalon API

[Unique-Divine]

Minor concern: Avalon API sometiems shows this error.

{"level":"error","error":"Get \"https://avalon-api-world.vercel.app/api/usda/susda-convert-ratio\": read tcp 192.168.1.100:56468->64.29.17.131:443: read: connection reset by peer","time":1756232908,"message":"failed to fetch prices from Avalon"}
{"level":"error","error":"Get \"https://avalon-api-world.vercel.app/api/usda/susda-convert-ratio\": read tcp 192.168.1.100:56468->64.29.17.131:443: read: connection reset by peer","time":1756232908,"message":"failed to update prices"}

This doesn't occur consistently enough to be concerning, but we can do better.

The sUSDa:USDa redeem ratio can be retrieve directly from Ethereum.