Create Portfolio Performance API Endpoints

[grantfox-oss]

Description:
Implement REST endpoints for accessing portfolio performance metrics and analytics data.

Acceptance Criteria:

• GET /api/portfolio/:id/performance - Overall metrics
• GET /api/portfolio/:id/allocation - Asset allocation
• GET /api/portfolio/:id/performance-history - Time series data
• GET /api/portfolio/:id/comparison - Benchmark comparison
• Support time range filtering (1M, 3M, 6M, 1Y, ALL)
• Response includes timestamp and calculation date
• Swagger documentation complete

Definition of Done:

• All endpoints implemented and tested
• Response time < 500ms
• Swagger documentation complete
• Data accuracy verified

Test Requirements:

• E2E tests for all endpoints
• Time range filtering tests
• Performance test

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[Kureszn]

I've reviewed the issue and believe I can contribute effectively. My experience spans software development, blockchain technologies, cybersecurity and open source collaboration. I take a structured approach to contributions carefully understanding the existing codebase, identifying the root cause and delivering a thoroughly tested implementation.

[barry01-hash]

I would love love to work on this issue

[grantfox-oss]

🦊 GrantFox — @Kureszn has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #33)
2. Your PR will be reviewed by the SourceXXL maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@Kureszn's PR #40 was approved and merged by @memplethee-lab.

🏆 @Kureszn: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (118 total points). Track your full progress on GrantFox.

👏 Great work, @Kureszn! Keep contributing to SourceXXL.