Adds two filter dropdowns next to the Search Expenses field (height-matched
to it): one filters by expense category, the other narrows to a single day.
Selecting a day shows a prominent summary banner with that day's total, and
hides the now-redundant per-day header. Both filters work on the desktop and
mobile layouts and compose with the existing search + all/mine/owed filters.
New i18n keys (costs.filter.allCategories / allDays, costs.expensesCount)
across every locale.
Maurice
bd2d91845b