Taiwan Business Tax Media File Export for AR/AP Invoices

Build a plugin that exports iDempiere AR and AP invoice data into the official Taiwan business tax media declaration file format (營業稅媒體申報檔). The plugin should read invoice records, tax amounts, and buyer/seller Unified Business Numbers (統一編號), then generate compliant media files ready for upload to the Taiwan Ministry of Finance e-filing system. Provide a Download button in the UI so users can export and save the generated file directly.