[Backend] — Extend `Match` entity with final scoreline & bonus points multiplier

[Olowodarey]

Background

`src/matches/entities/match.entity.

Goal

Add home_score, away_score, and points_multiplier to Match, write a
migration, and update the indexer to capture and persist them.

Tasks

1. Entity changes (src/matches/entities/match.entity.ts):
2. Migration: <timestamp>-AddScoreAndMultiplierToMatch.ts — adds the 3
3. Indexer — extractEventData() 'MatchAdded' case: add
4. Indexer — handleMatchAdded(): persist
5. Indexer — extractEventData() 'MatchResultSubmitted' case: add
6. Indexer — handleMatchResultSubmitted(): persist
7. ContractMatch interface (src/contract/contract.service.ts, lines
   28-36): add homeScore: number | null, awayScore: number | null,

Acceptance Criteria

• event_matches table has home_score, away_score (nullable
• A MatchAdded event with points_multiplier: 2 persists
• A MatchAdded event with points_multiplier: 5 (out of range)
• A MatchResultSubmitted event with home_score: 2, away_score: 1
• GET /matches/:id (matches.controller.ts) response includes