fix(attendance): payroll recap per accountant spec; multi-shift day rows; shared computation

Rekapitulace (accountant notes, confirmed by owner 2026-07):
- Odpracováno = all worked hours EXCEPT hours worked on holidays
  (was floor(worked/8)×8 — a 3h day printed as 0h)
- Vč. svátků a přesčasů = ALL worked hours; line2 − line1 = Svátek
  (was worked + vacation − 8h×worked-holidays — could print less than
  actually worked, and vacation inflated it)
- Přesčas = max(0, worked − fond), month-level, never negative
  (was the sub-8h remainder + vacation — printed 3h overtime for a
  3h month, 8h overtime for pure vacation, and −6h when a holiday
  was worked)
- Svátek = hours actually WORKED on holiday dates
  (was 8h per UNworked holiday — opposite meaning)
- So/Ne, Práce v noci, Dovolená, Fond unchanged (verified correct)

Single shared computeMzdaSummary now feeds BOTH the print and the
admin screen (they had drifted: capped vs uncapped holiday adjustment).

Print day table: one row PER RECORD — days with two shifts (real in
prod data) silently dropped all but the last record from the table
while the totals counted them all.

+7 spec tests (accountant's own examples); print snapshot updated to
the new spec values.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/admin/utils/attendanceHelpers.ts

@@ -370,3 +370,94 @@ export const calculateFreeHolidayHours = (
   }
   return free;
 };
+
+// ---------------------------------------------------------------------------
+// Mzda rekapitulace (single source — the print AND the admin screen consume
+// this, so the two can never drift again; spec confirmed with the accountant
+// 2026-07, see the summary lines below)
+// ---------------------------------------------------------------------------
+
+export interface MzdaSummary {
+  /** All worked hours in the month: arrival→departure minus recorded breaks. */
+  workedHoursRaw: number;
+  /** Odpracováno: all worked hours EXCEPT hours worked on public holidays. */
+  odpracovano: number;
+  /** Odpracováno včetně svátků a přesčasů: ALL worked hours (line2 − line1 = Svátek). */
+  vcetneSvatku: number;
+  /** Dovolená: sum of vacation leave_hours (hour-based, partial days allowed). */
+  vacationHours: number;
+  /** Přesčas: worked hours above the monthly fund — max(0, worked − fond). */
+  prescas: number;
+  /** Svátek: hours actually WORKED on public-holiday dates. */
+  svatekHours: number;
+  /** So/Ne: worked hours on Saturdays and Sundays. */
+  weekendHours: number;
+  /** Práce v noci: worked minutes in the 22:00–06:00 window. */
+  nightMinutes: number;
+  /** Fond měsíce: Mon–Fri (public holidays included) × 8 h. */
+  fund: number;
+  businessDays: number;
+  /** 8 h per holiday the user did NOT work (fond is covered by these). */
+  freeHolidayHours: number;
+}
+
+/** Compute the payroll recap for one user's month of records. */
+export const computeMzdaSummary = (
+  records: AttendanceRecord[],
+  monthStr: string,
+): MzdaSummary => {
+  const [yearStr, monthNumStr] = monthStr.split("-");
+  const yr = parseInt(yearStr, 10);
+  const mo = parseInt(monthNumStr, 10);
+
+  const holidayDates = holidaysInMonth(yr, mo);
+  const holidaySet = new Set(holidayDates);
+
+  let workedMinutes = 0;
+  let svatekMinutes = 0;
+  let weekendMinutes = 0;
+  let nightMinutes = 0;
+  let vacationHours = 0;
+
+  for (const r of records) {
+    const lt = r.leave_type || "work";
+    if (lt !== "work") {
+      if (lt === "vacation") vacationHours += Number(r.leave_hours) || 8;
+      continue;
+    }
+    const m = calculateWorkMinutesPrint(r);
+    workedMinutes += m;
+    const day = normalizeDateStr(r.shift_date);
+    if (holidaySet.has(day)) svatekMinutes += m;
+    if (isWeekendDate(day)) weekendMinutes += m;
+    nightMinutes += calculateNightMinutes(r);
+  }
+
+  // Fond: Mon–Fri × 8 h; public holidays stay in the count (they are paid via
+  // the fond — an unworked holiday earns its 8 h, see freeHolidayHours).
+  let businessDays = 0;
+  const cur = new Date(yr, mo - 1, 1);
+  while (cur.getMonth() === mo - 1) {
+    const dow = cur.getDay();
+    if (dow !== 0 && dow !== 6) businessDays++;
+    cur.setDate(cur.getDate() + 1);
+  }
+  const fund = businessDays * 8;
+
+  const workedHoursRaw = workedMinutes / 60;
+  const svatekHours = svatekMinutes / 60;
+
+  return {
+    workedHoursRaw,
+    odpracovano: workedHoursRaw - svatekHours,
+    vcetneSvatku: workedHoursRaw,
+    vacationHours,
+    prescas: Math.max(0, workedHoursRaw - fund),
+    svatekHours,
+    weekendHours: weekendMinutes / 60,
+    nightMinutes,
+    fund,
+    businessDays,
+    freeHolidayHours: calculateFreeHolidayHours(records, holidayDates),
+  };
+};