Fix RPC provider calls to avoid rate limiting

[schwepps]

Description

We're currently experiencing rate limiting issues with our RPC provider. This is causing intermittent failures in blockchain interactions and degrading the user experience.

Problem

Public RPC provider is rate limiting our requests
Our paid RPC endpoint is not used correctly

Proposed Solution

Implement a centralized RPC provider service with Nethermind

Acceptance Criteria

• Implement RPC provider with Nethermind
• [] Fallback to public provider

Priority

High