Expense budgets are stored signed-negative by budgetService. The Cartes
budget-adherence card used raw values in its filter (monthBudget > 0),
its in-target comparison (|actual| <= monthBudget), and its overrun
calculation — all of which silently rejected every expense row. Route
every amount through Math.abs() so the card reflects real budget data.
Test: regression fixture with a signed-negative monthBudget that must
pass the filter and count as in-target or overrun based on absolute
values.
Fixes#112
