* Add sync model
* Fresh fixtures for sync tests
* Sync tests overhaul
* Fix entry tests
* Complete remaining model test updates
* Update system tests
* Update demo data task
* Add system tests back to PR checks
* More simplifications, add empty family to fixtures for easier testing
* Support all currencies, handle outside DB
* Remove currencies from seed
* Fix account balance namespace
* Set default currency on authentication
* Cache currency instances
* Implement multi-currency syncs with tests
* Series fallback, passing tests
* Fix conflicts
* Make value group concrete class that works with currency values
* Fix migration conflict
* Update tests to expect multi-currency results
* Update account list to use group method
* Namespace updates
* Fetch unknown exchange rates from API
* Fix date range bug
* Ensure demo data works without external API
* Enforce cascades only at DB level
