Add campaign list table

[Errordog2]

Summary

• add a local campaign list table for browsing fake campaign records with sortable columns and selection controls
• add pure table helpers for row building, sort cycling, select all/clear/toggle, and selection summaries
• cover default updated sorting, name sorting, deterministic selection, valid-id filtering, and sort toggling with focused tests

Closes #282

Validation

px prettier --check src/features/demo-admin-dashboard/campaignListTable.ts src/features/demo-admin-dashboard/components/CampaignListTable.tsx src/features/demo-admin-dashboard/tests/campaignListTable.test.ts src/features/demo-admin-dashboard/index.ts

• git diff --check
• sensitive scan for account/payment/private-key markers returned no matches

px vitest run src/features/demo-admin-dashboard/tests/campaignListTable.test.ts could not start locally because this fresh checkout is missing the Vite config packages (@cloudflare/vite-plugin, @tailwindcss/vite, @tanstack/react-start/plugin/vite, @vitejs/plugin-react, �ite, �ite-tsconfig-paths)