fix: preserve fractional block volume

[nvphungdev]

Summary

• keep block-list volume as a Decimal value after converting from satoshis to BGL
• use the normal currency display path so sub-1-BGL values do not render as 0 in the table

Why

The block list was converting total_out + subsidy from satoshis to BGL and then applying parseInt, followed by a zero-decimal BGL formatter. Current Bitgesell block amounts can be below 1 BGL, so valid blockstats values were displayed as 0.

Closes #11

Validation

• npm test
• rendered views/includes/blocks-list.pug with mocked blockstats where subsidy is 596 sats and confirmed the volume cell renders fractional BGL instead of 0
• git diff --check

Note: npm run lint still reports existing unrelated errors across app/ and routes/; this PR only changes the Pug block-list template.