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/package.json

@@ -16,6 +16,8 @@
     "axios": "^1.17.0",
     "clsx": "^2.1.0",
     "framer-motion": "^12.40.0",
+    "html2canvas": "^1.4.1",
+    "jspdf": "^4.2.1",
     "lenis": "^1.3.23",
     "lucide-react": "^1.18.0",
     "next": "16.2.9",