Implement portfolio performance analytics (APY, Sharpe ratio, drawdown)

[robertocarlous]

Summary

Users can see current positions but have no historical performance view. Adding analytics calculations on YieldSnapshot data would unlock portfolio reporting.

Proposed Solution

Extend GET /api/analytics to return:

• Realized APY: annualised return from YieldSnapshot history
• Sharpe Ratio: risk-adjusted return (requires volatility calculation over snapshots)
• Max Drawdown: largest peak-to-trough decline in portfolio value
• Protocol Allocation %: breakdown by protocol

Compute in src/routes/analytics.ts using existing snapshot data; no new data collection needed.

Acceptance Criteria

• GET /api/analytics?period=30d|90d|1y returns metrics object
• APY calculation verified against manual calculation on test data
• Sharpe ratio uses risk-free rate from env var (default 0)
• Unit tests for each calculation function in src/utils/analytics.ts
• OpenAPI spec updated

[Kappa16]

@Kappa16 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Please maintainer..I can handle this professionally and make sure this issue is closed ASAP WITHOUT ERRORS.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Kappa16 to this issue.

[drips-wave]

Congratulations, @Kappa16! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Kappa16: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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