feat(web): add CSV export for reputation rankings in admin dashboard (closes #5)

[guptakumarranjeet150]

Summary of Changes

This PR implements the Export-to-CSV feature for reputation rankings on the admin dashboard, fulfilling all requirements specified in #5.

Key Implementations:

1. Shared Types (packages/types):

   • ReputationRanking: Standard model capturing contributor ranking, TrustScore, PRs merged, governance votes, and Drips stream allocations.
   • MonthlyReputationData: Aggregated DAO monthly rankings container.
   • CsvExportOptions: Configurable export options (toggle addresses, detailed metric breakdowns).

2. RFC-4180 Compliant CSV Generation (apps/web/src/utils/csvExport.ts):

   • generateReputationCsv(): Generates properly formatted and escaped CSV data.
   • escapeCsvField(): Adheres strictly to RFC-4180 rules (doubling internal quotes, wrapping values with commas/quotes/newlines).
   • generateMonthlyCsvFilename(): Sanitizes DAO names and periods (e.g. trustgraph_reputation_steward_dao_2026-09.csv).
   • triggerCsvDownload(): Cross-browser Blob download trigger.

3. Admin Dashboard Component (apps/web/src/components/AdminDashboard.tsx):

   • High-contrast, accessible UI displaying summary metrics (Total Contributors, Average TrustScore, PRs, Votes).
   • Evaluation Period selector (defaults to current month).
   • Instant Export-to-CSV button with download feedback toast.
   • Interactive options to toggle wallet address and detailed breakdown columns.

4. Comprehensive Test Suite:

   • apps/web/src/utils/csvExport.test.ts: 12 unit tests verifying escaping, sorting, option toggles, and edge cases.
   • apps/web/src/components/AdminDashboard.test.tsx: 4 component integration tests verifying render, export trigger, options, and period switching.
   • 16/16 tests pass green; tsc --noEmit typecheck passes with 0 errors.

Closes #5