[Backend] — Feature: Add `GET /predictions/market/:marketId` public predictions list

[Olowodarey]

Background

There is no public endpoint to list all predictions for a given market. Clients
wishing to show "who predicted what" on a market detail page must scrape private
user endpoints or go on-chain. A public, paginated endpoint is needed.

Goal

Add GET /predictions/market/:marketId returning paginated, anonymized
predictions for a market.

Requirements

1. In PredictionsService, add:

2. Add the route to PredictionsController:

Acceptance criteria

• Returns paginated results without exposing user IDs.
• Non-existent market returns empty list (not 404).

[gloskull]

Hello, I have 4 years of experience delivering solutions for projects like this, covering backend, frontend, and smart contract development. After carefully reviewing your requirements, I have a clear understanding of the task and am confident in my ability to deliver a clean, efficient, and thoroughly tested solution on time. I prioritize code quality, maintainability, and industry best practices throughout the development process.
My PR will be submitted in under 10hours.