feat: Add academic periods system for educational institutions

- Add AcademicPeriod model with support for schuljahr/semester/trimester
- Extend Event and EventMedia models with optional academic_period_id
- Create Alembic migration (8d1df7199cb7) for academic periods system
- Add init script for Austrian school year defaults (2024/25-2026/27)
- Maintain full backward compatibility for existing events/media
- Update program-info.json to version 2025.1.0-alpha.6

Database changes:
- New academic_periods table with unique name constraint
- Foreign key relationships with proper indexing
- Support for multiple period types with single active period

This lays the foundation for period-based organization of events
and media content, specifically designed for school environments
with future extensibility for universities.

dashboard/public/program-info.json

@@ -1,6 +1,6 @@
 {
   "appName": "Infoscreen-Management",
-  "version": "2025.1.0-alpha.5",
+  "version": "2025.1.0-alpha.6",
   "copyright": "© 2025 Third-Age-Applications",
   "supportContact": "support@third-age-applications.com",
   "description": "Eine zentrale Verwaltungsoberfläche für digitale Informationsbildschirme.",
@@ -26,10 +26,22 @@
     ]
   },
   "buildInfo": {
-    "buildDate": "2025-08-30T12:00:00Z",
-    "commitId": "a1b2c3d4e5f6"
+    "buildDate": "2025-09-20T11:00:00Z",
+    "commitId": "8d1df7199cb7"
   },
   "changelog": [
+    {
+      "version": "2025.1.0-alpha.6",
+      "date": "2025-09-20",
+      "changes": [
+        "🗓️ NEU: Akademische Perioden System - Unterstützung für Schuljahre, Semester und Trimester",
+        "🏗️ DATENBANK: Neue 'academic_periods' Tabelle für zeitbasierte Organisation",
+        "🔗 ERWEITERT: Events und Medien können jetzt optional einer akademischen Periode zugeordnet werden",
+        "📊 ARCHITEKTUR: Vollständig rückwärtskompatible Implementierung für schrittweise Einführung",
+        "🎯 BILDUNG: Fokus auf Schulumgebung mit Erweiterbarkeit für Hochschulen",
+        "⚙️ TOOLS: Automatische Erstellung von Standard-Schuljahren für österreichische Schulen"
+      ]
+    },
     {
       "version": "2025.1.0-alpha.5",
       "date": "2025-09-14",

dashboard/src/apiHolidays.ts

@@ -0,0 +1,26 @@
+export type Holiday = {
+  id: number;
+  name: string;
+  start_date: string;
+  end_date: string;
+  region?: string | null;
+  source_file_name?: string | null;
+  imported_at?: string | null;
+};
+
+export async function listHolidays(region?: string) {
+  const url = region ? `/api/holidays?region=${encodeURIComponent(region)}` : '/api/holidays';
+  const res = await fetch(url);
+  const data = await res.json();
+  if (!res.ok || data.error) throw new Error(data.error || 'Fehler beim Laden der Ferien');
+  return data as { holidays: Holiday[] };
+}
+
+export async function uploadHolidaysCsv(file: File) {
+  const form = new FormData();
+  form.append('file', file);
+  const res = await fetch('/api/holidays/upload', { method: 'POST', body: form });
+  const data = await res.json();
+  if (!res.ok || data.error) throw new Error(data.error || 'Fehler beim Import der Ferien');
+  return data as { success: boolean; inserted: number; updated: number };
+}

dashboard/src/appointments.tsx

@@ -144,7 +144,7 @@ const Appointments: React.FC = () => {
   const [modalInitialData, setModalInitialData] = useState({});
   const [schedulerKey, setSchedulerKey] = useState(0);
   const [editMode, setEditMode] = useState(false); // NEU: Editiermodus
-  const [showInactive, setShowInactive] = React.useState(false);
+  const [showInactive, setShowInactive] = React.useState(true);
 
   // Gruppen laden
   useEffect(() => {
@@ -413,7 +413,7 @@ const Appointments: React.FC = () => {
             }
             // Events nach Löschen neu laden
             if (selectedGroupId) {
-              fetchEvents(selectedGroupId)
+              fetchEvents(selectedGroupId, showInactive)
                 .then((data: RawEvent[]) => {
                   const mapped: Event[] = data.map((e: RawEvent) => ({
                     Id: e.Id,

dashboard/src/einstellungen.tsx

@@ -1,8 +1,83 @@
 import React from 'react';
-const Einstellungen: React.FC = () => (
-  <div>
-    <h2 className="text-xl font-bold mb-4">Einstellungen</h2>
-    <p>Willkommen im Infoscreen-Management Einstellungen.</p>
-  </div>
-);
+import { listHolidays, uploadHolidaysCsv, type Holiday } from './apiHolidays';
+
+const Einstellungen: React.FC = () => {
+  const [file, setFile] = React.useState<File | null>(null);
+  const [busy, setBusy] = React.useState(false);
+  const [message, setMessage] = React.useState<string | null>(null);
+  const [holidays, setHolidays] = React.useState<Holiday[]>([]);
+
+  const refresh = React.useCallback(async () => {
+    try {
+      const data = await listHolidays();
+      setHolidays(data.holidays);
+    } catch (e) {
+      const msg = e instanceof Error ? e.message : 'Fehler beim Laden der Ferien';
+      setMessage(msg);
+    }
+  }, []);
+
+  React.useEffect(() => {
+    refresh();
+  }, [refresh]);
+
+  const onUpload = async () => {
+    if (!file) return;
+    setBusy(true);
+    setMessage(null);
+    try {
+      const res = await uploadHolidaysCsv(file);
+      setMessage(`Import erfolgreich: ${res.inserted} neu, ${res.updated} aktualisiert.`);
+      await refresh();
+    } catch (e) {
+      const msg = e instanceof Error ? e.message : 'Fehler beim Import.';
+      setMessage(msg);
+    } finally {
+      setBusy(false);
+    }
+  };
+
+  return (
+    <div>
+      <h2 className="text-xl font-bold mb-4">Einstellungen</h2>
+      <div className="space-y-4">
+        <section className="p-4 border rounded-md">
+          <h3 className="font-semibold mb-2">Schulferien importieren</h3>
+          <p className="text-sm text-gray-600 mb-2">
+            Laden Sie eine CSV-Datei mit den Spalten: <code>name</code>, <code>start_date</code>,{' '}
+            <code>end_date</code>, optional <code>region</code>.
+          </p>
+          <div className="flex items-center gap-3">
+            <input
+              type="file"
+              accept=".csv,text/csv"
+              onChange={e => setFile(e.target.files?.[0] ?? null)}
+            />
+            <button className="e-btn e-primary" onClick={onUpload} disabled={!file || busy}>
+              {busy ? 'Importiere…' : 'CSV importieren'}
+            </button>
+          </div>
+          {message && <div className="mt-2 text-sm">{message}</div>}
+        </section>
+
+        <section className="p-4 border rounded-md">
+          <h3 className="font-semibold mb-2">Importierte Ferien</h3>
+          {holidays.length === 0 ? (
+            <div className="text-sm text-gray-600">Keine Einträge vorhanden.</div>
+          ) : (
+            <ul className="text-sm list-disc pl-6">
+              {holidays.slice(0, 20).map(h => (
+                <li key={h.id}>
+                  {h.name}: {h.start_date} – {h.end_date}
+                  {h.region ? ` (${h.region})` : ''}
+                </li>
+              ))}
+            </ul>
+          )}
+        </section>
+      </div>
+    </div>
+  );
+};
+
 export default Einstellungen;