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.

gscript/Setup.js

@@ -0,0 +1,128 @@
+function setupSystem() {
+  const props = PropertiesService.getScriptProperties();
+  let id = props.getProperty('DB_SPREADSHEET_ID');
+  let ss;
+
+  if (id) {
+    ss = SpreadsheetApp.openById(id);
+  } else {
+    ss = SpreadsheetApp.create('MeStaff Database');
+    props.setProperty('DB_SPREADSHEET_ID', ss.getId());
+  }
+
+  Object.keys(CFG.SHEETS).forEach(k => {
+    const name = CFG.SHEETS[k];
+    let s = ss.getSheetByName(name);
+    if (!s) s = ss.insertSheet(name);
+    const headers = HEADERS[k];
+    if (s.getLastRow() === 0) s.getRange(1,1,1,headers.length).setValues([headers]);
+    s.setFrozenRows(1);
+    s.getRange(1,1,1,headers.length).setFontWeight('bold');
+  });
+
+  const defaultSheet = ss.getSheetByName('Sheet1') || ss.getSheetByName('List1');
+  if (defaultSheet && Object.values(CFG.SHEETS).indexOf(defaultSheet.getName()) === -1) {
+    ss.deleteSheet(defaultSheet);
+  }
+
+  if (!props.getProperty('PASSWORD_PEPPER')) {
+    props.setProperty('PASSWORD_PEPPER', Utilities.getUuid() + Utilities.getUuid());
+  }
+
+  seedSettings_();
+  return {ok:true, spreadsheetId:ss.getId(), url:ss.getUrl()};
+}
+
+function seedSettings_() {
+  const current = rows_(CFG.SHEETS.SETTINGS);
+  const map = {};
+  current.forEach(r => map[r.key] = r.value);
+  const defaults = {
+    APP_NAME: 'MeStaff',
+    CURRENCY: 'CZK',
+    TIMEZONE: CFG.TZ,
+    NIGHT_START: '22:00',
+    NIGHT_END: '06:00'
+  };
+  Object.keys(defaults).forEach(k => {
+    if (map[k] === undefined) append_(CFG.SHEETS.SETTINGS, {key:k, value:defaults[k]});
+  });
+}
+
+function seedFirstAdmin(email, firstName, lastName) {
+  email = emailNorm_(email);
+  if (!email) throw new Error('Zadej e-mail.');
+  const lock = LockService.getScriptLock();
+  lock.waitLock(10000);
+  try {
+    let company = findOne_(CFG.SHEETS.COMPANIES, r => r.active === true || String(r.active).toUpperCase() === 'TRUE');
+    if (!company) {
+      company = {company_id:'COMPANY_MAIN', name:'Hlavní společnost', ico:'', active:true};
+      append_(CFG.SHEETS.COMPANIES, company);
+    }
+    let loc = findOne_(CFG.SHEETS.LOCATIONS, r => String(r.company_id) === String(company.company_id));
+    if (!loc) {
+      loc = {location_id:'LOCATION_MAIN', company_id:company.company_id, name:'Hlavní provozovna', active:true};
+      append_(CFG.SHEETS.LOCATIONS, loc);
+    }
+    let emp = findOne_(CFG.SHEETS.EMPLOYEES, r => emailNorm_(r.email) === email);
+    if (!emp) {
+      emp = {
+        employee_id: uuid_('EMP'),
+        first_name:firstName || 'Admin',
+        last_name:lastName || '',
+        email,
+        company_id:company.company_id,
+        location_id:loc.location_id,
+        position:'Administrátor',
+        employment_type:'',
+        terminal_pin:'',
+        start_date:isoDate_(now_()),
+        end_date:'',
+        active:true
+      };
+      append_(CFG.SHEETS.EMPLOYEES, emp);
+    }
+    let user = findOne_(CFG.SHEETS.USERS, r => emailNorm_(r.email) === email);
+    if (!user) {
+      user = {
+        user_id:uuid_('USR'),
+        email,
+        role:'ADMIN',
+        employee_id:emp.employee_id,
+        password_salt:'',
+        password_hash:'',
+        active:true,
+        created_at:now_(),
+        last_login:''
+      };
+      append_(CFG.SHEETS.USERS, user);
+    }
+    return {ok:true, email, message:'Admin založen. Teď použij „Aktivovat účet“ na přihlašovací stránce.'};
+  } finally {
+    lock.releaseLock();
+  }
+}
+
+function createSystemTriggers() {
+  ScriptApp.getProjectTriggers().forEach(t => {
+    if (['nightlyMaintenance','monthlyMaintenance'].includes(t.getHandlerFunction())) {
+      ScriptApp.deleteTrigger(t);
+    }
+  });
+
+  ScriptApp.newTrigger('nightlyMaintenance')
+    .timeBased().everyDays(1).atHour(3).inTimezone(CFG.TZ).create();
+
+  ScriptApp.newTrigger('monthlyMaintenance')
+    .timeBased().onMonthDay(1).atHour(4).inTimezone(CFG.TZ).create();
+
+  return {ok:true};
+}
+function createMyAdmin() {
+  return seedFirstAdmin(
+    'filip.thurrigl@gmail.com',
+    'Philipp',
+    'Thürrigl'
+  );
+}