Fix/supp ag fb (#1023)

* fix: prevent credit notes from entering payment flow

* fix: persist and display customer personal numbers

* feat: configure automatic invoice reminder days

* fix: issue credit notes through send flow

* chore: add repository agent guidance

* feat(mcp): route tools across user companies

* fix(articles): delete unused register entries

* feat(invoices): improve issued invoice actions

* feat(supplier-invoices): retain uploaded source documents

* docs: record implementation decisions

* feat: enhance customer personal number handling and validation

- Updated CustomerForm to allow personal numbers in the format of "********-1234" for individual customers.
- Added validation to ensure personal numbers are only accepted for individual customers in CreateCustomerSchema.
- Implemented masking and encryption for personal numbers to enhance data protection.
- Introduced new utility functions for masking and encrypting personal numbers.
- Added database migration to enforce unique constraints on credit note relationships and prevent duplicate entries.
- Enhanced error handling and logging for credit note issuance and invoice processing.
- Updated tests to cover new credit note creation guards and personal number handling.

* test: enhance list companies test with supabase query mocks

lib/customers/mask-personal-number.ts

@@ -0,0 +1,8 @@
+/**
+ * Display a personal identity number without exposing birth date or full ID.
+ */
+export function maskCustomerPersonalNumber(value: string | null | undefined): string | null {
+  if (!value) return null
+  const last4 = value.replace(/\D/g, '').slice(-4)
+  return last4.length === 4 ? `********-${last4}` : null
+}

lib/customers/protect-personal-number.ts

@@ -0,0 +1,21 @@
+import { decryptPersonnummer, encryptPersonnummer } from '@/lib/salary/personnummer'
+import { maskCustomerPersonalNumber } from '@/lib/customers/mask-personal-number'
+
+export function encryptCustomerPersonalNumber(value: string | null | undefined): string | null {
+  return value ? encryptPersonnummer(value) : null
+}
+
+export function maskStoredCustomerPersonalNumber(value: string | null | undefined): string | null {
+  if (!value) return null
+  if (/^(\d{6}|\d{8})[-+]?\d{4}$/.test(value)) {
+    return maskCustomerPersonalNumber(value)
+  }
+  return maskCustomerPersonalNumber(decryptPersonnummer(value))
+}
+
+export function maskCustomerRow<T extends { personal_number?: string | null }>(row: T): T {
+  return {
+    ...row,
+    personal_number: maskStoredCustomerPersonalNumber(row.personal_number),
+  }
+}