Feature: Implement lending pool performance tracking with historical returns

[devdianax]

Context

Lenders need historical performance data to evaluate pool profitability and make investment decisions.

Current Limitation/Problem

No historical return tracking exists. Users cannot evaluate pool performance over time.

Expected Outcome

A performance tracking system that records pool APY, utilization, bad debt, and liquidity over time with configurable granularity.

Acceptance Criteria

• Capture hourly snapshots: TVL, utilization, borrow APY, supply APY, bad debt
• Aggregated metrics: 7d, 30d, 90d, 1y averages and volatility
• Performance chart: cumulative returns, APY trend, utilization heatmap
• Event tracking: liquidation events, bad debt events, parameter changes
• Performance comparison across pools with ranking
• Export performance data as CSV for external analysis
• Benchmarking against DeFi lending benchmarks (Compound, Aave rates)

Technical Scope

• backend/src/services/analytics/pool-performance.ts
• Prisma: PoolSnapshot, PoolPerformance models
• BullMQ cron for hourly snapshots
• Frontend: performance charts and comparison UI
• Edge cases: new pools with short history, data gaps from network downtime