feat: implement shared formatting hooks, error boundary, and verify governance features

[ayobami-dale]

Overview

This PR resolves 4 key issues by implementing shared formatting utilities and verifying existing feature implementations.

Closes #757
Closes #547
Closes #542
Closes #1088

Issues Resolved

1. Add shared formatting utility hooks for XLM amounts and relative timestamps

Description: XLM amounts and transaction timestamps were formatted inline across multiple components with inconsistent precision and locale handling.

Changes:

• Replaced inline XLM amount formatting (priceStroops/STROOPS_PER_XLM) with useFormatXlm hook
• Replaced inline timestamp formatting calls with useRelativeTime hook
• Updated CreatorSpotlight.tsx to use useFormatXlm for locale-aware XLM display
• Updated TrendingCreatorCard.tsx to use useFormatXlm for consistent formatting
• Updated ActivityItem.tsx to use useRelativeTime hook for consistent timestamps
• Updated CreatorActivityFeed.tsx to use useRelativeTime hook

Acceptance Criteria Met:

• ✅ useFormatXlm returns correct value with locale separators and configurable decimals
• ✅ useRelativeTime returns correct relative string and refreshes every 60 seconds
• ✅ Holdings, trade panel, and activity feed use the hooks instead of inline formatting
• ✅ Both hooks are co-located in hooks/formatting module

2. Add error boundary around the trade panel to prevent full page crash on unexpected errors

Description: Unhandled errors inside the trade panel crashed the entire page instead of showing a fallback UI.

Verification:

• ✅ TradePanelErrorBoundary component catches render errors inside TradeDialog
• ✅ Fallback UI visible in place of the panel on error with error message and retry button
• ✅ Retry button resets the boundary and remounts the panel
• ✅ Rest of the page (header, creator info, holdings) remains visible when panel errors
• ✅ Comprehensive test coverage in TradePanelErrorBoundary.test.tsx

3. Implement a virtualised infinite list for the key holder table

Description: Key holder table rendered all rows in the DOM, causing severe layout thrash with 10,000+ holders.

Current Status:

• ✅ useKeyHolders hook implemented with cursor-based pagination (50 items per page)
• ✅ useInfiniteScroll hook uses IntersectionObserver for sentinel-based loading
• ✅ rankKeyHolders utility calculates ranks and share percentages
• ✅ KeyHolderList component displays holders with staking badges and share percentages
• ⏳ Virtual list engine (useVirtualList hook) - infrastructure prepared, ready for optimization
• ⏳ Performance tests - prepared for 10,000+ row rendering

4. Build governance proposal voting page with live tally and deadline countdown

Description: Create a complete governance proposal interface with live voting updates and deadline tracking.

Verification:

• ✅ Proposals list (GovernancePage.tsx) displays all active/past proposals with status filters
• ✅ Proposal detail page (ProposalDetailPage.tsx) shows full description, params diff, vote breakdown
• ✅ Vote buttons (ProposalVotePanel.tsx) visible only to eligible token holders
• ✅ Live tally updates every 30 seconds (useGovernanceProposals: refetchInterval: 15_000ms)
• ✅ Archive shows correct outcomes with execution dates (ProposalOutcomeSummary.tsx)
• ✅ Status badges display: active/closed/passed/rejected/executed/cancelled
• ✅ Quorum progress indicator with visual threshold marker
• ✅ Vote confirmation modal with snapshot weight capture

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