feat(realunit): overhaul transaction receipt PDF

[TaprootFreak]

Summary

• Language override: Receipt DTOs (RealUnitSingleReceiptPdfDto, RealUnitMultiReceiptPdfDto) now accept an optional language parameter so the app can request receipts in the user's current locale
• Enhanced RealUnit description: Receipts use the official designation "RealUnit Namenaktie (Aktientoken REALU), ISIN CH1137233305 — Registerwertrecht via Ethereum-Blockchain" (i18n in DE/EN/FR/IT)
• New receipt fields: Unit price per share, fee disclosure ("spesenfrei"), execution date+time, buyer name, wallet address, full tx hash, and payment method — rendered in a details section below the table
• Layout improvements: Uses creditor city (Baar) instead of hardcoded "Zug", adds unit price column to table when available

Context

Requested by RealUnit Schweiz AG (Dani Stüssi) to bring transaction receipts in line with their corporate template and Swiss financial standards.

Changed files

File	Change
realunit-pdf.dto.ts	Add optional language?: PdfLanguage to both receipt DTOs
{de,en,fr,it}/invoice.json	Add realunit_receipt i18n section (13 keys each)
swiss-qr.service.ts	Extend SwissQRBillTableData, add drawReceiptDetails(), refactor generatePdfInvoice + generateMultiPdfInvoice for REALUNIT brand
realunit.controller.ts	Pass dto.language and jwt.address to service methods

Test plan

• Generate single receipt PDF via POST /v1/realunit/transactions/receipt/single with language: "DE" — verify German description with ISIN, unit price column, details section
• Generate multi-receipt PDF via POST /v1/realunit/transactions/receipt/multi — verify per-transaction unit prices and shared details section
• Generate receipt without language param — verify fallback to user profile language
• Verify non-RealUnit (DFX brand) invoices are unchanged
• Verify all 4 language variants render correctly (DE/EN/FR/IT)