fix: guard pool metrics against NaN/Infinity/undefined values (fixes #6)

[jiangyj545]

Problem

Issue #6 reports that pool performance metrics show incorrect or nonsensical numbers.

Root Cause Analysis

Three categories of bugs in src/components/pool/Pools.svelte:

1. Division by zero in feeAPY: setFeeAPYs() divides by _balances[asset] without checking if the value is > 0. When balance is 0, undefined, or not yet loaded → Infinity or NaN displayed as APY %.

2. No null-safety on store values: $globalUPLs[asset], $bufferBalances[asset], $poolStakes[asset] are rendered directly via numberWithCommas(). Before stores populate (or for missing assets) these are undefined → displays raw "undefined" or misleading "0".

3. Loose equality in % of Pool: Uses == 0 instead of > 0 check, meaning falsy values slip through.

Fix

• Added > 0 guard in setFeeAPYs() — only calculates APY when balance is positive
• Added safeMetric() helper — returns "-" for undefined/null/NaN/Infinity values
• Applied safeMetric() to all 6 metric cells: Balance, Fee APY, Trader UP/L, Buffer, Your Balance
• Changed % of Pool from == 0 to > 0 strict check

Changes

File	Change
src/components/pool/Pools.svelte	+16/-10: null-safety guards + safeMetric helper

Build

✅ npx rollup -c passes cleanly (only pre-existing warnings)