Intro now focuses on billable hours as the sole KPI metric rather than
specific numbers. Calculator moved below the critique section. Removed
the "8h work = 6.5 billable" item (too specific for the new tone).
Show the full calculation as a written equation:
365 - 52x2=104 Wochenendtage - Urlaub - Feiertage = Arbeitstage.
Fixes "104 Wochenenden" → "52 x 2 = 104 Wochenendtage".
Interactive calculator: enter annual hours target + vacation days,
shows actual billable hours per working day after subtracting weekends,
vacation, and public holidays. Makes the absurdity of 2400h targets visible.
