- expense_kind enum (utilities + maintenance/repair/cleaning/insurance/tax/rent/other)
- property_expenses table with optional link to a property_accounts row
(preserves history via ON DELETE SET NULL)
- services/expenses.ts: CRUD + 12-month monthly series aggregation +
year-to-date summary by kind
- /properties/[id]/expenses tab: inline SVG line chart for electricity +
water last 12 months (no chart library), summary card, add/edit/delete
inline with account linking when kind matches
