Add daily expense tracking with sort/split and CSV export

Standalone expenses (date, description, category, amount) with the same
equal/own/payer split machinery as entry costs, merged into the costs
panel and settle-up as a single expense bucket. Self-fetching card
with per-day grouping, client-side sorting, and quick-add. CSV export
interleaves expenses with priced entries, one share column per member
(UTF-8 BOM, RFC 4180, formula-injection guard on text cells).

Also fixes trip deletion, which hit a foreign-key violation and rolled
back for any trip with checklist items.

tests/index.js

@@ -10,6 +10,9 @@ import './api.test.js';
 import './checklist.test.js';
 import './checklist-suggestions.test.js';
 import './costs.test.js';
+import './expense-csv.test.js';
+import './expenses.test.js';
+import './expenses-export.test.js';
 import './flights.test.js';
 import './rental.test.js';
 import './stays.test.js';