feat: implement GET /bounties/recommended with weighted matching

[autonomy414941]

Summary

• add new GET /bounties/recommended endpoint for authenticated users
• score open bounties against the user's tech_stack using weighted tag matching and return relevanceScore
• cache per-user recommendations for 15 minutes to avoid repeated DB work
• wire bounties route into createApp()
• add focused API tests for auth handling, ranking behavior, limit validation, and cache reuse

Validation

• npm test -- src/__tests__/bounties.test.ts
• npm run typecheck

Fixes #22

[devasign-app]

❌ PR Review Failed

---

Error Details

The PR review system encountered an error while analyzing this pull request:

Review failed: Failed to parse AI response into JSON. Please review manually.

What to do next

1. Manual Review: Please proceed with manual code review
2. Retry: You can manually trigger a new analysis if the issue was temporary
3. Support: If this error persists, please contact support

---

🤖 This is an automated error message from the PR review system.

💬 Need help? Open an issue or contact support.