feat(dashboard): fix #8 replace vault leaderboard placeholder with in…

[Owolabenjade]

Summary

• Replaces static placeholder component (components/app/VaultLeaderboardPlaceholder.jsx) with a production-grade, indexed saver leaderboard (VaultLeaderboard).
• Defines TypeScript domain contracts in types/leaderboard.ts (LeaderboardEntry, LeaderboardFilterOptions, LeaderboardResponse, RankState).
• Implements orchestration service in services/leaderboardService.ts providing API data fetching, deterministic score sorting (sortLeaderboardEntries), local dev fallback, and privacy-conscious address formatting (formatPrivacyAddress for Stellar GABC...XYZ and EVM 0x12...5678).
• Exposes backend indexed saver endpoint GET /actions/leaderboard in backend/src/routes/actions.ts.
• Supports full UI state lifecycle: loading skeleton, error retry banner, empty state, and visual rank badges (build(deps): update soroban-sdk requirement from 21 to 27 in /contracts #1 gold, Fix invalid root package.json scripts block so pnpm install and CI can parse the workspace #2 silver, Remove committed .rej patch artifacts and prevent rejected patch files from returning #3 bronze).
• Adds unit tests in components/app/VaultLeaderboard.test.jsx testing sorting order, address formatting, and UI state rendering.

Linked Issue

• Fixes Replace vault leaderboard placeholder with real indexed leaderboard data and loading/error states #8

Validation

• npm run lint
• npm run build
• pnpm audit run for dependencies
• No raw secrets committed
• Additional contract/backend checks listed below when applicable
  • Ran npx vitest run components/app/VaultLeaderboard.test.jsx (All address formatting, score sorting, and UI state tests passed).

Notes

• Replaces placeholder UI with live indexed saver analytics driven by transaction data.
• Includes local dev fallback when backend indexer APIs are offline.
• No new environment variables, contract deployments, or breaking database schema changes required.

[BigDella]

@Owolabenjade great job love this