Feature/fee collected event - #385

closes #329

This PR implements the handling for the fee_collected contract event and introduces treasury fee reporting for administrators. It also resolves several underlying build and type-related issues in the backend to ensure a successful production build.

Key Features

1. Fee Event Indexing & Real-time Updates

• Event Handler: Implemented handleFeeCollected in SorobanEventWorker to decode and persist fee_collected events emitted during stream creation and top-ups.
• Real-time SSE: Integrated sseService.broadcastToAdmin to notify administrative subscribers immediately when a protocol fee is collected.
• Processing Order Safety: Updated the event worker to sort incoming events within a batch, ensuring stream_created events are always processed before fee_collected events to maintain database integrity and foreign key constraints.

2. Administrative Metrics

• Treasury Reporting: Extended the /v1/admin/metrics endpoint to provide aggregated fee statistics.
• Token-based Aggregation: Admins can now see total fees collected per token and a specific breakdown for the last 24-hour window.

Technical Fixes & Improvements

• Build Resolution: Fixed a syntax error in soroban-event-worker.ts (extra closing brace) and resolved an ioredis import conflict for ESM compatibility in redis.ts.
• Type Safety:
  • Defined proper Request parameter types in stream.controller.ts to fix address property access errors.
  • Exported SSEService class to support named imports in the test suite.
  • Added proper type casting for mocked Prisma methods in stream.test.ts to satisfy TypeScript requirements.
• Code Quality: All new logic is implemented without additional comments, maintaining the project's existing code style.

Acceptance Criteria Verified

• fee_collected events are written to the StreamEvent table.
• Admin metrics include fee totals per token and per 24h window.
• Real-time stream.fee_collected SSE events are broadcast to admins.
• Existing event handlers remain unaffected.
• npm run build completes successfully.