* perf(dashboard): streamline investment activity totals
* fix(dashboard): skip empty investment totals cache writes
Short-circuit empty investment account totals before cache fetch and move the new SQL query capture regression helper into test/support.
* refactor(dashboard): address review on investment totals query
- Drop defensive ArgumentError guards in InvestmentStatement::Totals#initialize.
The sole caller (totals_query) always passes correct types, and the
empty_result early-return already handles the zero-accounts case.
- Remove the redundant accounts JOIN and its family_id/status filters from the
aggregation SQL. account_ids is already scoped to the family's visible
(draft/active) investment accounts, so the join back to accounts is
unnecessary work in the query plan. Drop the now-unused family_id param.
- Add a regression assertion that the aggregate no longer joins accounts.
