Add shift planning, month closure + payroll, and a dark modern redesign

Ports two modules from the friend's Google Apps Script build (kept as
reference in gscript/) onto the TypeScript stack, rewritten cleanly against
this app's own data model rather than copied 1:1:

- Shift planning: weekly template (Sun-Thu evening, Fri/Sat two slots),
  lazy idempotent generation per period (no cron needed), employee
  signup/cancel with collision + capacity checks, admin calendar view with
  slot editing and manual assignment.
- Month closure + payroll: employee confirms the month (blocked while a
  shift is still open), admin locks and finalizes pay (base hours * rate +
  tips/bonus/other), reopen to undo a premature lock, mark paid. Pay rates
  are versioned by date, defaulting the first-ever rate to apply
  retroactively to the employee's whole history.
- A shift left open more than 12h (forgotten clock-out) is auto-closed at
  clock_in + 12h, checked lazily on read instead of a background job.
- Full dark, sharp-edged modern restyle (theme.css replaces tui.css) with
  an amber accent, keeping every existing class name so no component
  logic needed to change.

Backend test coverage (jest) for all three workflows: shift planning,
closure/payroll, and the forgotten-clock-out auto-close.

backend/src/services/payroll.ts

@@ -0,0 +1,188 @@
+import { db } from "../db";
+import type { ClosureStatus, Payroll, PayrollStatus } from "../types";
+import { findClosure, getClosureSummary, lockClosure } from "./closure";
+import { listEmployees } from "./employees";
+import { todayIso } from "../util/date";
+
+export interface PayrollAdjustments {
+  tips_amount: number;
+  bonus_amount: number;
+  other_amount: number;
+}
+
+export function findPayroll(employeeId: number, period: string): Payroll | undefined {
+  return db
+    .prepare<[number, string], Payroll>("SELECT * FROM payroll WHERE employee_id = ? AND period = ?")
+    .get(employeeId, period);
+}
+
+/** Manager-side draft (tips/bonus/other) prepared before the month is locked. Frozen once locked. */
+export function saveDraftAdjustments(employeeId: number, period: string, adjustments: PayrollAdjustments): Payroll {
+  const closure = findClosure(employeeId, period);
+  if (!closure || closure.status === "waiting_employee") {
+    throw new Error("Odměny lze zadat až po potvrzení docházky zaměstnancem.");
+  }
+  const existing = findPayroll(employeeId, period);
+  if (existing && existing.status !== "draft") {
+    throw new Error("Mzdový podklad už byl uzamčen a nelze jej tímto způsobem měnit.");
+  }
+  for (const value of Object.values(adjustments)) {
+    if (!Number.isFinite(value)) {
+      throw new Error("Částka musí být číslo.");
+    }
+  }
+
+  const summary = getClosureSummary(employeeId, period);
+  const finalAmount =
+    summary.earned_estimate + adjustments.tips_amount + adjustments.bonus_amount + adjustments.other_amount;
+
+  upsertPayroll(employeeId, period, {
+    worked_minutes: summary.worked_minutes,
+    base_amount: summary.earned_estimate,
+    tips_amount: adjustments.tips_amount,
+    bonus_amount: adjustments.bonus_amount,
+    other_amount: adjustments.other_amount,
+    final_amount: finalAmount,
+    status: "draft",
+  });
+
+  return findPayroll(employeeId, period)!;
+}
+
+/** Locks the month closure and freezes the payroll numbers (whatever draft adjustments existed, or zero). */
+export function lockAndFinalizePayroll(employeeId: number, period: string): Payroll {
+  lockClosure(employeeId, period);
+
+  const summary = getClosureSummary(employeeId, period);
+  const draft = findPayroll(employeeId, period);
+  const tips = draft?.tips_amount ?? 0;
+  const bonus = draft?.bonus_amount ?? 0;
+  const other = draft?.other_amount ?? 0;
+  const finalAmount = summary.earned_estimate + tips + bonus + other;
+
+  upsertPayroll(employeeId, period, {
+    worked_minutes: summary.worked_minutes,
+    base_amount: summary.earned_estimate,
+    tips_amount: tips,
+    bonus_amount: bonus,
+    other_amount: other,
+    final_amount: finalAmount,
+    status: "ready",
+  });
+
+  return findPayroll(employeeId, period)!;
+}
+
+/** Undoes a lock that turned out to be premature (e.g. the rate wasn't set yet) — back to an editable draft. */
+export function reopenPayroll(employeeId: number, period: string): Payroll {
+  const closure = findClosure(employeeId, period);
+  const payroll = findPayroll(employeeId, period);
+  if (!closure || closure.status !== "locked" || !payroll || payroll.status !== "ready") {
+    throw new Error("Lze odemknout jen uzamčenou a dosud nevyplacenou mzdu.");
+  }
+
+  db.prepare("UPDATE month_closures SET status = 'confirmed', locked_at = NULL WHERE id = ?").run(closure.id);
+
+  const summary = getClosureSummary(employeeId, period);
+  const finalAmount = summary.earned_estimate + payroll.tips_amount + payroll.bonus_amount + payroll.other_amount;
+  upsertPayroll(employeeId, period, {
+    worked_minutes: summary.worked_minutes,
+    base_amount: summary.earned_estimate,
+    tips_amount: payroll.tips_amount,
+    bonus_amount: payroll.bonus_amount,
+    other_amount: payroll.other_amount,
+    final_amount: finalAmount,
+    status: "draft",
+  });
+
+  return findPayroll(employeeId, period)!;
+}
+
+export function markPaid(employeeId: number, period: string): Payroll {
+  const payroll = findPayroll(employeeId, period);
+  if (!payroll || payroll.status !== "ready") {
+    throw new Error("Mzda musí být nejdřív uzamčena.");
+  }
+
+  db.prepare(
+    "UPDATE payroll SET status = 'paid', payment_date = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%fZ', 'now') WHERE id = ?"
+  ).run(todayIso(), payroll.id);
+
+  return findPayroll(employeeId, period)!;
+}
+
+export interface PayrollOverviewRow {
+  employee_id: number;
+  employee_name: string;
+  closure_status: ClosureStatus;
+  worked_minutes: number;
+  base_amount: number;
+  tips_amount: number;
+  bonus_amount: number;
+  other_amount: number;
+  final_amount: number;
+  payroll_status: PayrollStatus | null;
+  payment_date: string | null;
+}
+
+export function getPeriodOverview(period: string): PayrollOverviewRow[] {
+  return listEmployees()
+    .filter((employee) => employee.active === 1)
+    .map((employee) => {
+      const closure = findClosure(employee.id, period);
+      const payroll = findPayroll(employee.id, period);
+      const summary = payroll ? null : getClosureSummary(employee.id, period);
+
+      return {
+        employee_id: employee.id,
+        employee_name: employee.name ?? employee.email,
+        closure_status: closure?.status ?? "waiting_employee",
+        worked_minutes: payroll?.worked_minutes ?? summary!.worked_minutes,
+        base_amount: payroll?.base_amount ?? summary!.earned_estimate,
+        tips_amount: payroll?.tips_amount ?? 0,
+        bonus_amount: payroll?.bonus_amount ?? 0,
+        other_amount: payroll?.other_amount ?? 0,
+        final_amount: payroll?.final_amount ?? summary!.earned_estimate,
+        payroll_status: payroll?.status ?? null,
+        payment_date: payroll?.payment_date ?? null,
+      };
+    });
+}
+
+function upsertPayroll(
+  employeeId: number,
+  period: string,
+  data: {
+    worked_minutes: number;
+    base_amount: number;
+    tips_amount: number;
+    bonus_amount: number;
+    other_amount: number;
+    final_amount: number;
+    status: PayrollStatus;
+  }
+): void {
+  db.prepare(
+    `INSERT INTO payroll (employee_id, period, worked_minutes, base_amount, tips_amount, bonus_amount, other_amount, final_amount, status, updated_at)
+     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))
+     ON CONFLICT (employee_id, period) DO UPDATE SET
+       worked_minutes = excluded.worked_minutes,
+       base_amount = excluded.base_amount,
+       tips_amount = excluded.tips_amount,
+       bonus_amount = excluded.bonus_amount,
+       other_amount = excluded.other_amount,
+       final_amount = excluded.final_amount,
+       status = excluded.status,
+       updated_at = excluded.updated_at`
+  ).run(
+    employeeId,
+    period,
+    data.worked_minutes,
+    data.base_amount,
+    data.tips_amount,
+    data.bonus_amount,
+    data.other_amount,
+    data.final_amount,
+    data.status
+  );
+}