add: feiertage

static/app.css

@@ -681,6 +681,33 @@ footer {
   border-color: #4da3ff;
 }
 
+.calendar-day-sunday,
+.calendar-day-holiday {
+  background: #fff7f7;
+}
+
+.calendar-day-today.calendar-day-sunday,
+.calendar-day-today.calendar-day-holiday {
+  background: linear-gradient(135deg, #f7fbff 0%, #f7fbff 60%, #fff2f2 100%);
+}
+
+.calendar-day-sunday .calendar-day-header,
+.calendar-day-holiday .calendar-day-header {
+  color: #b93838;
+}
+
+.calendar-holiday-badge {
+  display: inline-block;
+  margin-left: 6px;
+  padding: 2px 8px;
+  border-radius: 999px;
+  background: #ffe3e3;
+  color: #b93838;
+  font-size: 0.75rem;
+  font-weight: 700;
+  white-space: nowrap;
+}
+
 .calendar-day:last-child {
   border-bottom: none;
 }

templates/calendar_section.html

@@ -91,6 +91,63 @@
     return `${year}-${month}-${day}`;
   };
 
+  const holidayCache = new Map();
+
+  function calculateEasterSunday(year) {
+    const a = year % 19;
+    const b = Math.floor(year / 100);
+    const c = year % 100;
+    const d = Math.floor(b / 4);
+    const e = b % 4;
+    const f = Math.floor((b + 8) / 25);
+    const g = Math.floor((b - f + 1) / 3);
+    const h = (19 * a + b - d - g + 15) % 30;
+    const i = Math.floor(c / 4);
+    const k = c % 4;
+    const l = (32 + 2 * e + 2 * i - h - k) % 7;
+    const m = Math.floor((a + 11 * h + 22 * l) / 451);
+    const month = Math.floor((h + l - 7 * m + 114) / 31);
+    const day = ((h + l - 7 * m + 114) % 31) + 1;
+    return new Date(year, month - 1, day);
+  }
+
+  function getGermanHolidays(year) {
+    if (holidayCache.has(year)) return holidayCache.get(year);
+
+    const holidays = new Map();
+    const add = (month, day, name) => {
+      holidays.set(toLocalISO(new Date(year, month - 1, day)), name);
+    };
+
+    add(1, 1, 'Neujahr');
+    add(5, 1, 'Tag der Arbeit');
+    add(10, 3, 'Tag der Deutschen Einheit');
+    add(12, 25, '1. Weihnachtstag');
+    add(12, 26, '2. Weihnachtstag');
+
+    const easterSunday = calculateEasterSunday(year);
+    const addOffset = (offset, name) => {
+      const d = new Date(easterSunday);
+      d.setDate(easterSunday.getDate() + offset);
+      holidays.set(toLocalISO(d), name);
+    };
+
+    addOffset(-2, 'Karfreitag');
+    addOffset(0, 'Ostersonntag');
+    addOffset(1, 'Ostermontag');
+    addOffset(39, 'Christi Himmelfahrt');
+    addOffset(49, 'Pfingstsonntag');
+    addOffset(50, 'Pfingstmontag');
+
+    holidayCache.set(year, holidays);
+    return holidays;
+  }
+
+  function getHolidayName(date) {
+    const holidays = getGermanHolidays(date.getFullYear());
+    return holidays.get(toLocalISO(date)) || '';
+  }
+
   function getCalendarRange() {
     const weeks = window._calendarIsAdmin ? 12 : 4;
     const start = new Date();
@@ -121,6 +178,9 @@
       const date = new Date(start);
       date.setDate(start.getDate() + i);
       const isoDate = toLocalISO(date);
+      const isSunday = date.getDay() === 0;
+      const holidayName = getHolidayName(date);
+      const holidayBadge = holidayName ? `<span class="calendar-holiday-badge">${holidayName}</span>` : '';
 
       const dayBlock = document.createElement('div');
       dayBlock.className = 'calendar-day empty';
@@ -128,11 +188,17 @@
       if (isoDate === toLocalISO(new Date())) {
         dayBlock.classList.add('calendar-day-today');
       }
+      if (isSunday) {
+        dayBlock.classList.add('calendar-day-sunday');
+      }
+      if (holidayName) {
+        dayBlock.classList.add('calendar-day-holiday');
+      }
 
       dayBlock.innerHTML = `
         <div class="calendar-day-header">
           <div class="calendar-day-name">${formatDayName.format(date)}</div>
-          <div class="calendar-day-date">${formatDate.format(date)}</div>
+          <div class="calendar-day-date">${formatDate.format(date)}${holidayBadge}</div>
         </div>
         <div class="table-responsive calendar-table-wrapper">
           <table class="table table-sm mb-0">