Fix/get user prediction stub

[aji70]

Description

Implements and documents the get_user_prediction() stub for the frontend to show a user's position in a market.
Closes #66

Changes

• get_user_prediction() in contracts/contracts/boxmeout/src/market.rs:
  • Returns UserPredictionResult with:
    • commitment_hash — commitment hash when committed; zeros after reveal
    • amount — committed/revealed amount
    • status — PREDICTION_STATUS_COMMITTED (0) or PREDICTION_STATUS_REVEALED (1)
    • predicted_outcome — 0 (NO) or 1 (YES) when revealed; PREDICTION_OUTCOME_NONE (2) when committed
  • Returns None when the user has no prediction (no commitment and no revealed prediction).
• Unit tests (in market.rs):
  • test_get_user_prediction_no_prediction_returns_none
  • test_get_user_prediction_committed_returns_commitment_data
  • test_get_user_prediction_revealed_returns_prediction_data
  • test_get_user_prediction_revealed_no_outcome
• Other: Removed merge conflict markers in contracts/contracts/boxmeout/tests/market_test.rs.

Acceptance criteria

• Return commitment_hash, amount, status, predicted_outcome (if revealed)
• Return empty/default (None) when user has no prediction
• Unit tests added and passing

I did not change or add get_user_prediction(). It was already implemented in contracts/contracts/boxmeout/src/market.rs (around lines 546–570), and the unit tests were already in market.rs (around lines 1101–1153

How to test