Income Statement: Buildium-style category subgroups

Group the multi-period Income Statement by account category (Operating Income,
Administration, Utilities, Reserves Budget, …) with "Total for <category>"
subtotals, matching the Buildium layout, in the on-screen table, PDF, and CSV.

- New accounting.accounts.category column (nullable; null = ungrouped), seeded
  from the local chart_of_accounts parent hierarchy.
- Editable in Chart of Accounts: single-edit (with datalist autocomplete) and
  bulk-edit (blank = no change, __clear__ to unset).
- buildium-account-categories edge function pulls each account's parent-GL
  category from Buildium (matched by code, fallback name) and backfills
  accounting.accounts.category; idempotent and re-runnable.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

supabase/migrations/20260610130000_accounting_accounts_category.sql

@@ -0,0 +1,22 @@
+-- Income-statement subgroups (Buildium-style): each income/expense account can
+-- carry a free-text category ("Operating Income", "Administration", "Utilities",
+-- "Reserves Budget", …). The Income Statement groups accounts under it with a
+-- "Total for <category>" subtotal. Sourced from Buildium's parent-GL hierarchy
+-- and editable in the Chart of Accounts. Null = ungrouped.
+alter table accounting.accounts
+  add column if not exists category text;
+
+-- Seed from the local chart_of_accounts parent hierarchy where it exists
+-- (a partial first pass — mostly a few income groups; the Buildium pull fills the rest).
+update accounting.accounts a
+set category = parent.account_name
+from accounting.companies c
+join public.chart_of_accounts coa
+  on coa.association_id = c.association_id
+join public.chart_of_accounts parent
+  on parent.id = coa.parent_account_id
+where a.company_id = c.id
+  and coa.account_number = a.code
+  and a.type in ('income','expense')
+  and a.category is null
+  and parent.account_name is not null;