Blog categories (hasMany), shipping-address contact fields, product SKU on invoices

- Posts.categories is now hasMany — blog list/detail/live-preview render
  a comma-joined list instead of a single category.
- Checkout's "Abweichende Lieferadresse" gains optional Firma + Kontakt-
  E-Mail/Telefon fields (handed to the shipping carrier, not used for
  customer communication).
- Customer profile can now store its own shipping address (mirroring
  Customers.ts's new "Lieferadresse" tab), prefilling the checkout
  override instead of always starting blank.
- Product-level optional SKU (previously only on variants) snapshots onto
  each order item and shows up on invoices (visual + EN16931 XML),
  the confirmation email, and the account order detail page.

package-lock.json

@@ -455,8 +455,8 @@
       }
     },
     "node_modules/@einfach-produktiv/invoicing": {
-      "version": "0.2.6",
-      "resolved": "git+https://git.mk360.de/Marco/einfach-produktiv-invoicing.git#d6e83db5cf6343e65e2fa25f9ead49fce9a5a308",
+      "version": "0.2.7",
+      "resolved": "git+https://git.mk360.de/Marco/einfach-produktiv-invoicing.git#e66007cc4aacccf3b1f18892f3ae9a5e6adf685e",
       "dependencies": {
         "@e-invoice-eu/core": "^3.1.1"
       },