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

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

app/api/v1/companies/[companyId]/accounts/route.ts

@@ -23,6 +23,8 @@ const Account = z.object({
   is_active: z.boolean(),
   description: z.string().nullable(),
   default_vat_code: z.string().nullable(),
+  default_vat_rate: z.number().nullable(),
+  default_vat_treatment: z.string().nullable(),
   sru_code: z.string().nullable(),
   sort_order: z.number().int(),
 })
@@ -32,7 +34,7 @@ const AccountsResponse = dataEnvelope(z.object({ accounts: z.array(Account) }))
 const ACCOUNT_COLUMNS =
   'account_number, account_name, account_class, account_group, account_type, ' +
   'normal_balance, is_system_account, is_active, description, default_vat_code, ' +
-  'sru_code, sort_order'
+  'default_vat_rate, default_vat_treatment, sru_code, sort_order'
 
 registerEndpoint({
   operation: 'accounts.list',