Pick up critical e-invoice fix: shipping/discount degross bug + BR-CO-25

Every AllowanceCharge (shipping/discount) generated since the integer-cents pipeline landed was ~19%/7% too large — the /(1+rate/100) degross step was silently dropped in that rewrite. Real impact confirmed on a real order via an external checker: PayableRoundingAmount was showing >1 EUR instead of a normal few-cents residual. Also adds PrepaidAmount/PaymentTerms handling for BR-CO-25. Bumps to git.mk360.de/Marco/einfach-produktiv-invoicing@f6d8e9e.

package-lock.json

@@ -359,7 +359,7 @@
     },
     "node_modules/@einfach-produktiv/invoicing": {
       "version": "0.1.0",
-      "resolved": "git+https://git.mk360.de/Marco/einfach-produktiv-invoicing.git#fd5d8e688b1ab6b13dfd734e194a780b8a2b12d2",
+      "resolved": "git+https://git.mk360.de/Marco/einfach-produktiv-invoicing.git#f6d8e9eaf55e3a6ce3ca4b8246d5a8ed3dac7d02",
       "dependencies": {
         "@e-invoice-eu/core": "^3.1.1"
       },