Add governance homepage presentational components

[Copilot]

Adds standalone governance homepage UI components for the planned Governance Widget. Scope stays presentational: mocked data, no wallet, contract, subgraph, or runtime integration.

• Governance widget package

  • Added @goodwidget/governance-widget
  • Exports ImpactCard, BalanceCard, AlignmentVotingProposalCard, OptimisticVotingProposalCard, and FundingDistributionChart
  • Keeps governance-only helpers local to the package

• Component coverage

  • Impact metrics with static and streaming amounts
  • Token/raw balance displays with growth or time-window metadata
  • Alignment vote cards with ranked options and capped visible rows
  • Optimistic vote cards with quorum summary, stacked vote bar, voter previews, and legends
  • Funding distribution donut chart with allocation legend and empty state

• Demo and smoke coverage

  • Added Storybook stories under governance-widget
  • Added Playwright smoke specs and screenshot evidence under tests/widgets/governance-widget/

Example usage:

<ImpactCard
  title="Community impact this month"
  metrics={[
    { label: 'Distributed', amount: { value: 348000, token: 'G$' } },
    { label: 'Streaming now', amount: { value: 12800, token: 'G$', isStreaming: true } },
  ]}
  description="Track how governance funding turns into measurable activity."
  ctaLabel="View impact report"
/>