feat: add payer reputation marketplace filter

[newmattock]

Fixes #31

Summary

• add a Min Payer Reputation slider to the LP marketplace filter panel
• filter already-loaded marketplace invoices client-side using fetched payer scores
• persist the reputation threshold in localStorage for returning LPs
• show the payer score next to each marketplace risk badge
• add regression coverage for minimum payer reputation filtering and fix the stale root test import plus Vitest alias

Validation

• npm test -- tests/invoiceFilters.test.ts --reporter verbose
• npx eslint src/hooks/useInvoiceFilters.ts src/components/InvoiceFilterBar.tsx tests/invoiceFilters.test.ts vitest.config.ts
• npm run build
• git diff --check
• local smoke: HEAD /lp returned HTTP 200 on port 3016

Note: full-file lint for src/components/LPDashboard.tsx still reports pre-existing no-explicit-any/react-hooks issues outside this focused change.