feat(fusion_accounting_reports): seed 3 partner-grouped reports

Adds Aged Receivable, Aged Payable, and Partner Ledger as fusion.report
records using the new compute_partner_grouped engine method.

REPORT_TYPES is extended with aged_receivable / aged_payable /
partner_ledger so each report has a unique report_type. The HTTP
controller dispatches these to engine.compute_partner_grouped with
the appropriate account_type via PARTNER_GROUPED_ACCOUNT_TYPE.

Output includes per-partner aging buckets: current, 1-30, 31-60,
61-90, 90+ days.

Westin total: 4 + 4 + 3 = 11 of Enterprise's 22 standard reports.

Made-with: Cursor

fusion_accounting_reports/models/fusion_report.py

@@ -13,6 +13,9 @@ REPORT_TYPES = [
     ('balance_sheet', 'Balance Sheet'),
     ('trial_balance', 'Trial Balance'),
     ('general_ledger', 'General Ledger'),
+    ('aged_receivable', 'Aged Receivable'),
+    ('aged_payable', 'Aged Payable'),
+    ('partner_ledger', 'Partner Ledger'),
 ]