feat: Thai VAT schemes as Sales/Purchase Taxes and Charges Templates

Per Thai company: Thailand VAT 7%, Thailand VAT 7% (Included) for
VAT-inclusive pricing, Thailand VAT 0% for zero-rated supplies. Sales
schemes post to Output VAT, purchase schemes to Input VAT (category
Total, so recoverable VAT stays out of valuation). The 7% scheme is the
default when the company has none. Created on Company save, after
install, and by a patch for existing companies.

default_thai_company/hooks.py

@@ -103,7 +103,8 @@ fixtures = [
 # ------------
 
 # before_install = "default_thai_company.install.before_install"
-# after_install = "default_thai_company.install.after_install"
+# Fixtures are synced before this runs; VAT schemes for companies that already exist.
+after_install = "default_thai_company.vat.setup_companies"
 
 # Uninstallation
 # ------------
@@ -167,7 +168,10 @@ doc_events = {
 		"before_import": "default_thai_company.tax_withholding.prepare_fixture_accounts",
 	},
 	"Company": {
-		"on_update": "default_thai_company.tax_withholding.setup_company",
+		"on_update": [
+			"default_thai_company.tax_withholding.setup_company",
+			"default_thai_company.vat.setup_company",
+		],
 	},
 	"Payment Entry": {
 		"validate": "default_thai_company.tax_withholding.set_customer_withholding",