Make Net APY the headline rate metric

[Sikkra]

Closes #28

Summary

• Adds gross supply APR and fee-drag APR to reserve/projected rate data, plus a shared netAprBreakdown helper for the requested supply + blndSupply + blndBorrow - borrow - feeDrag calculation.
• Makes Net APY the selected asset headline metric and moves raw rate components into a collapsed expander.
• Updates projected APY chart, position metrics, portfolio cards, overview table, and demo reserves to consume the same breakdown consistently.

Verification

• npm run build (passes; existing Vite chunk-size warning remains)
• git diff --check
• npx tsc --noEmit (still fails on existing repo config/API type issues: .ts import extension settings and AuthModalParams.network; the new APY helper has no remaining type errors)
• Local Edge/Playwright fallback on http://127.0.0.1:5203/: demo mode rendered Net APY +6.50% at 28px, raw APR grid hidden outside the expander, component expander closed by default and opened with Supply/BLND/Borrow/Fee Drag rows, portfolio card Net APY +8.11%, browser errors 0.

Note: the Codex in-app browser pane was unavailable in this session, so I used the local Edge/Playwright fallback for UI verification.