feat(invoices): Persian line items + elegant client-side PDF download

- Translate persisted English invoice line labels/descriptions/reasons to
  Persian at display time (new lib/invoice-labels.ts), covering both new and
  historical invoices without a data migration.
- Generate a styled, RTL Persian invoice PDF on the client (lib/invoice-pdf.ts)
  with the Abrban logo, line-item table and totals, via html2canvas + jsPDF.
- Wire both the user and admin invoice pages to the translator and new download.
- Add invoices.pdf dictionary keys (fa/en).
- Remove the now-dead ASCII-only backend PDF endpoints and generateInvoicePdf.
- Add frontend/.npmrc (npmmirror registry + high timeouts) for Iran-network installs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/i18n/dictionaries/en.ts

@@ -705,6 +705,21 @@ const en: Dictionary = {
       statusUpdated: 'Invoice status updated',
       statusUpdateFailed: 'Failed to update invoice status',
       reasonRequired: 'Reason is required for manual status changes',
+      pdf: {
+        documentTitle: 'Invoice',
+        tagline: 'Cloud infrastructure, in your control',
+        invoiceNumberLabel: 'Invoice number',
+        colIndex: '#',
+        colDesc: 'Description',
+        colAmount: 'Amount',
+        customer: 'Customer',
+        application: 'Application',
+        createdAt: 'Issued on',
+        paidAt: 'Paid on',
+        subtotal: 'Subtotal',
+        generatedAt: 'This document was generated automatically on {date}.',
+        footer: 'Abrban — abrban.com',
+      },
     },
     logs: {
       title: 'Logs',