feat(accounting): Kostenstellen von Eingangsbelegen jederzeit nachträglich ändern

Eigener Endpunkt und MCP-Tool ändern ausschließlich die Positionskostenstellen,
auch bei gebuchten oder einer Bankbuchung zugewiesenen Eingangsbelegen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/pages/incomingInvoices/[mode]/[id].vue

@@ -200,6 +200,47 @@ const getAccountLabel = (item) => {
   return account ? `${account.number || ""} ${account.label || ""}`.trim() : "-"
 }
 const getCostCentreLabel = (item) => costcentres.value.find((costcentre) => costcentre.id === item.costCentre)?.name || "-"
+
+const canEditCostCentres = computed(() => mode.value === "show" && Boolean(itemInfo.value.id) && !itemInfo.value.archived)
+const costCentresOpen = ref(false)
+const costCentresSaving = ref(false)
+const costCentreDraft = ref([])
+const costCentreOptionLabel = (id) => {
+  const centre = costcentres.value.find((item) => item.id === id)
+  return centre ? [centre.number, centre.name].filter(Boolean).join(" - ") : (id ? "Bisherige Kostenstelle" : "Keine Kostenstelle")
+}
+
+const openCostCentres = () => {
+  costCentreDraft.value = (itemInfo.value.accounts || []).map((account, index) => ({
+    index,
+    label: `${index + 1}. ${account.description || getAccountLabel(account)}`,
+    costcentre: account.costCentre || null,
+  }))
+  costCentresOpen.value = true
+}
+
+const saveCostCentres = async () => {
+  if (costCentresSaving.value) return
+  costCentresSaving.value = true
+  try {
+    const accountCostCentres = costCentreDraft.value
+        .filter((row) => row.costcentre !== (itemInfo.value.accounts[row.index]?.costCentre || null))
+        .map(({ index, costcentre }) => ({ index, costcentre }))
+    if (accountCostCentres.length) {
+      const { invoice } = await useNuxtApp().$api(`/api/functions/incoming-invoices/${itemInfo.value.id}/cost-centres`, {
+        method: "PUT",
+        body: { accountCostCentres },
+      })
+      itemInfo.value.accounts = normalizeIncomingInvoiceAccounts(invoice.accounts || [], invoice.date)
+      toast.add({ title: "Kostenstellen gespeichert", color: "success" })
+    }
+    costCentresOpen.value = false
+  } catch (error) {
+    toast.add({ title: "Kostenstellen konnten nicht gespeichert werden", description: error?.data?.error || "Bitte versuche es erneut.", color: "error" })
+  } finally {
+    costCentresSaving.value = false
+  }
+}
 const getBookingModeLabel = (item) => EXPENSE_BOOKING_MODE_ITEMS.find((mode) => mode.value === item.bookingMode)?.label || "-"
 const getTaxLabel = (item) => taxOptions.value.find((tax) => tax.key === item.taxType)?.label || "-"
 
@@ -362,6 +403,14 @@ const hasBlockingIncomingInvoiceErrors = computed(() => blockingIncomingInvoiceE
       >
         Bearbeiten
       </UButton>
+      <UButton
+          v-if="canEditCostCentres"
+          icon="i-heroicons-tag"
+          variant="outline"
+          @click="openCostCentres"
+      >
+        Kostenstellen bearbeiten
+      </UButton>
       <ArchiveButton
           v-if="canArchiveIncomingInvoice"
           color="error"
@@ -1060,6 +1109,27 @@ const hasBlockingIncomingInvoiceErrors = computed(() => blockingIncomingInvoiceE
     </div>
   </div>
 
+  <UModal v-model:open="costCentresOpen" title="Kostenstellen bearbeiten" :dismissible="!costCentresSaving" :close="!costCentresSaving" :ui="{ content: 'sm:max-w-2xl' }">
+    <template #body>
+      <p class="mb-4 text-sm text-muted">Die Kostenstellen der Positionen können jederzeit geändert werden, auch bei gebuchten oder zugewiesenen Belegen. Alle anderen Angaben bleiben unverändert.</p>
+      <div class="space-y-4">
+        <UFormField v-for="row in costCentreDraft" :key="row.index" :label="row.label">
+          <InputGroup>
+            <USelectMenu v-model="row.costcentre" :items="costcentres" value-key="id" label-key="name" :filter-fields="['name', 'number']" class="w-full" :disabled="costCentresSaving">
+              <template #default>{{ costCentreOptionLabel(row.costcentre) }}</template>
+              <template #item="{ item }">{{ [item.number, item.name].filter(Boolean).join(' - ') }}</template>
+            </USelectMenu>
+            <UButton icon="i-heroicons-x-mark" variant="outline" :aria-label="`Kostenstelle für ${row.label} entfernen`" :disabled="costCentresSaving || !row.costcentre" @click="row.costcentre = null" />
+          </InputGroup>
+        </UFormField>
+      </div>
+    </template>
+    <template #footer>
+      <UButton variant="outline" :disabled="costCentresSaving" @click="costCentresOpen = false">Abbrechen</UButton>
+      <UButton :loading="costCentresSaving" @click="saveCostCentres">Kostenstellen speichern</UButton>
+    </template>
+  </UModal>
+
 </template>
 
 <style scoped>