fix(vat): complete account treatment enforcement (#1593)

* fix(vat): complete account treatment enforcement

* docs(api): refresh account endpoint skill

* fix(mcp): preserve ruta 05 compatibility

* test(vat): seed migration constraint fixtures

* docs(vat): clarify treatment precedence

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/api/__tests__/schemas.test.ts

@@ -1996,23 +1996,6 @@ describe('CreateAccountSchema', () => {
     })
     expect(result.success).toBe(false)
   })
-
-  it('rejects a VAT treatment that does not apply to the account class', () => {
-    expect(CreateAccountSchema.safeParse({
-      account_number: '5010',
-      account_name: 'Consulting costs',
-      account_type: 'expense',
-      normal_balance: 'debit',
-      default_vat_treatment: 'standard_25',
-    }).success).toBe(false)
-    expect(CreateAccountSchema.safeParse({
-      account_number: '5010',
-      account_name: 'EU services',
-      account_type: 'expense',
-      normal_balance: 'debit',
-      default_vat_treatment: 'reverse_charge_eu_services',
-    }).success).toBe(true)
-  })
 })
 
 // ============================================================
@@ -2327,6 +2310,9 @@ describe('UpdateAccountSchema', () => {
     expect(UpdateAccountSchema.safeParse({
       default_vat_treatment: 'reverse_charge_eu_goods',
     }).success).toBe(true)
+    expect(UpdateAccountSchema.safeParse({
+      default_vat_treatment: 'reverse_charge_non_eu_services',
+    }).success).toBe(true)
     expect(UpdateAccountSchema.safeParse({ default_vat_treatment: null }).success).toBe(true)
     expect(UpdateAccountSchema.safeParse({ default_vat_treatment: 'eu_purchase' }).success).toBe(false)
   })