refactor(postgres): port Trial Balance report query to the query builder

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

erpnext/accounts/report/trial_balance/trial_balance.py

@@ -4,7 +4,7 @@
 
 import frappe
 from frappe import _
-from frappe.query_builder.functions import Sum
+from frappe.query_builder.functions import Max, Sum
 from frappe.utils import add_days, cstr, flt, formatdate, getdate
 
 import erpnext
@@ -82,12 +82,21 @@ def validate_filters(filters):
 
 
 def get_data(filters):
-	accounts = frappe.db.sql(
-		"""select name, account_number, parent_account, account_name, root_type, report_type, is_group, lft, rgt
-
-		from `tabAccount` where company=%s order by lft""",
-		filters.company,
-		as_dict=True,
+	accounts = frappe.get_all(
+		"Account",
+		filters={"company": filters.company},
+		fields=[
+			"name",
+			"account_number",
+			"parent_account",
+			"account_name",
+			"root_type",
+			"report_type",
+			"is_group",
+			"lft",
+			"rgt",
+		],
+		order_by="lft",
 	)
 	company_currency = filters.presentation_currency or erpnext.get_company_currency(filters.company)
 
@@ -240,7 +249,8 @@ def get_opening_balance(
 		frappe.qb.from_(closing_balance)
 		.select(
 			closing_balance.account,
-			closing_balance.account_currency,
+			# account_currency is constant per grouped account -> Max() keeps the GROUP BY postgres-valid
+			Max(closing_balance.account_currency).as_("account_currency"),
 			Sum(closing_balance.debit).as_("debit"),
 			Sum(closing_balance.credit).as_("credit"),
 			Sum(closing_balance.debit_in_account_currency).as_("debit_in_account_currency"),