Invoice archive with search & regeneration

[therealjhay]

ProblemInvoiceGenerator and BatchInvoiceDownload exist but invoices are generated ad-hoc with no archive, search, or regeneration.

Solution

• Add app/(merchant)/settlement/invoices/page.tsx listing generated invoices with date, settlement ids, amounts, and file status.
• Store invoice metadata in localStorage (or backend when available) and allow regeneration from stored settlement data.
• Add a batch header/date filter and full-text search across business names/ids.
• Wire filename generation to a date + invoice number (sanitized) instead of raw ids.

Acceptance Criteria

• Regenerating an invoice reproduces identical amounts from stored snapshots.
• Search filters the archive correctly.
• Filenames are unique and sanitized.
• npm run build passes.

Note for Contributors: Write a clear PR description. Show archive search and regeneration.