feat(alerts): add price alerts management endpoints with jwt auth and ownership validation

[chiomailekuba]

closes #867

Summary of Changes

Implements price alert management endpoints with full JWT authentication, authorization, and validation:

• Created PriceAlert entity and repository handling alert rules (asset, targetPrice, direction: ABOVE/BELOW, status: ACTIVE/TRIGGERED/CANCELLED).
• Built Alert Controller and Service with CRUD operations:
  • POST /api/v1/alerts: Create a new price alert with threshold validation.
  • GET /api/v1/alerts: List alerts belonging to the authenticated user.
  • DELETE /api/v1/alerts/:id: Delete an alert with strict ownership checks (403/404 if not owned).
  • PATCH /api/v1/alerts/:id: Update alert parameters or toggle status.
• Added input validation middleware using schemas ensuring positive target prices and valid direction enums.
• Added integration test suite in src/modules/alerts/__tests__/alert.test.ts covering creation, listing, unauthorized access, cross-user isolation, and threshold checks.

Testing & Verification

• Ran npm test -- src/modules/alerts/__tests__/alert.test.ts: all 15 integration tests passing.
• TypeScript build and lint clean.

[drips-wave]

@chiomailekuba Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits