Add function to retrieve company address as JSON and update invoice procedures

- Created a new function `fds__getCompanyAddressJson` to return a company's postal address as a structured JSON object.
- Modified stored procedures `fds__createInvoice`, `fds__setInvoice`, and `fds__prepInvoice` to include a new parameter `@SendToAddressJson` for handling the address data.
- Updated the invoice table and user-defined types to accommodate the new `SendToAddressJson` field.
- Ensured that the address data is properly retrieved and stored in the invoice records.

Fuchs/Docs/INVOICE_LIFECYCLE.md

@@ -90,8 +90,12 @@ payload; see `EVAL_live_invoice_editing.md` for the rationale.
 ### 4.1 What the user can change
 - **Line items** — quantities, prices, notes, combine into one sum
   (`$inv.rendersrq`, `$inv.quantChange`).
-- **Recipient fields** — invoice title, address, email, provision
-  location/period (inline edit fields, `fm(...)` helper in `fis.inv_shared.js`).
+- **Recipient fields** — invoice title, email, provision location/period (inline
+  edit fields, `fm(...)` helper in `fis.inv_shared.js`). The **recipient address**
+  is edited via a **structured dialog** (`$inv.eAddress`: name, street, PLZ, city,
+  country, optional VAT id) prefilled from `fds__prepInvoice`'s `invoiceaddressData`;
+  it drives the EN 16931 eRechnung and composes the free-text `SendToAddress` for the
+  PDF (see [`Concepts/erechnung-output.md`](Concepts/erechnung-output.md)).
 - **§13b reverse-charge** toggle (`$inv.sp13b`) — suppresses VAT lines/columns.
 - **Set-pricing display mode** (`$inv.ssetmode` / `setSetmode`) — `SetPrice`
   (default) / `SetOnly`; see `INVOICE_SET_PRICING.md`. Purely presentational
@@ -360,6 +364,10 @@ flowchart TD
 - **Draft vs. final changes the rendered PDF**: draft = watermark overlay, no
   GiroCode; final = no watermark, GiroCode payment QR added when there's a
   positive balance.
+- **Final invoices can be emitted as eRechnung**: when `Fuchs:ERechnung:Enabled`,
+  the final PDF is a ZUGFeRD/Factur-X **PDF/A-3 hybrid** (eRechnungLib embeds the
+  CII XML into the render-only visual PDF; any failure falls back to the plain
+  PDF/A). Off by default. See [`Concepts/erechnung-output.md`](Concepts/erechnung-output.md).
 - **Email is best-effort and tracked**: `IsSent` is only set `true`
   automatically after a *successful* send; a failed send still leaves a
   correctly finalised, stored invoice that staff can resend or mark sent