fix: handle missing proposal vote counts

[Globalpropertyguy]

Summary

• Fix votePercentage when older proposals omit one or more vote-count rows
• Sum the vote-count rows returned by the chain instead of assuming indexes 0, 1, and 2 always exist
• Return 0.00 safely when no vote weight is available

Fixes #184.

Verification

• git diff --check
• Ran a Node smoke check using the proposal Stake Age updates #1 vote-count shape from the issue: [{ key: 0, value: 58 }, { key: 1, value: 164 }] -> total 222, yes percentage 73.87

Notes

• I did not run the project lint/build because this repo pins Node 14/npm 6 in package.json, while the available local environment is Node 24/npm 11.