feat: Serientermin-Bearbeitung: Nur diesen Termin oder Serie

Klick auf einen wiederkehrenden Termin oeffnet zuerst einen Dialog:
"Nur diesen Termin" oder "Ganze Serie".

* Serie: bearbeitet den Master wie bisher
* Nur dieser: fuegt EXDATE fuer das geklickte Datum zum Master
  hinzu und legt einen eigenstaendigen Ersatz-Termin mit den
  bearbeiteten Daten an

Backend:
* CalendarEvent.exdates speichert Ausnahmedaten kommasepariert
* POST /events/<id>/exception fuegt EXDATE hinzu, erstellt
  optional das Replacement-Event mit frischer UID
* _build_vevent schreibt jetzt EXDATE-Zeilen in die ical_data,
  sodass CalDAV-Clients die Ausnahmen auch sehen werden

Frontend:
* FullCalendar rrule-Plugin bekommt die exdate-Liste und blendet
  die uebersprungenen Tage aus
* Drag & Drop verschiebt weiterhin die ganze Serie (Shortcut -
  fuer Einzelverschiebung Termin anklicken und bearbeiten)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/calendar.py

@@ -171,7 +171,7 @@ def create_event(cal_id):
     rrule = (data.get('recurrence_rule') or '').strip()
 
     ical_data = _build_ical(event_uid, summary, dtstart_dt, dtend_dt, all_day,
-                            description, location, rrule)
+                            description, location, rrule, None)
 
     event = CalendarEvent(
         calendar_id=cal_id,
@@ -226,13 +226,87 @@ def update_event(event_id):
     event.ical_data = _build_ical(
         event.uid, event.summary, event.dtstart, event.dtend,
         event.all_day, event.description or '', event.location or '',
-        event.recurrence_rule or ''
+        event.recurrence_rule or '',
+        event.exdates.split(',') if event.exdates else None,
     )
     event.updated_at = datetime.now(timezone.utc)
     db.session.commit()
     return jsonify(event.to_dict()), 200
 
 
+@api_bp.route('/events/<int:event_id>/exception', methods=['POST'])
+@token_required
+def add_event_exception(event_id):
+    """Exclude a single occurrence of a recurring event ("nur dieser Termin").
+    Optionally creates a standalone replacement event for that date."""
+    user = request.current_user
+    event = db.session.get(CalendarEvent, event_id)
+    if not event:
+        return jsonify({'error': 'Event nicht gefunden'}), 404
+
+    cal, err = _get_calendar_or_err(event.calendar_id, user, need_write=True)
+    if err:
+        return err
+    if not event.recurrence_rule:
+        return jsonify({'error': 'Kein Serientermin'}), 400
+
+    data = request.get_json()
+    occurrence_date = data.get('occurrence_date')  # ISO date or datetime
+    if not occurrence_date:
+        return jsonify({'error': 'occurrence_date erforderlich'}), 400
+
+    # Normalize to YYYY-MM-DD for storage key
+    try:
+        parsed = datetime.fromisoformat(occurrence_date.replace('Z', '+00:00'))
+        key = parsed.strftime('%Y-%m-%d' if event.all_day else '%Y-%m-%dT%H:%M:%S')
+    except ValueError:
+        key = occurrence_date
+
+    existing = (event.exdates or '').split(',') if event.exdates else []
+    if key not in existing:
+        existing.append(key)
+    event.exdates = ','.join(filter(None, existing))
+
+    # Optional: create replacement single event
+    replacement = None
+    if data.get('replacement'):
+        r = data['replacement']
+        rep_uid = str(uuid.uuid4())
+        rep_start = datetime.fromisoformat(r['dtstart'])
+        rep_end = datetime.fromisoformat(r['dtend']) if r.get('dtend') else rep_start
+        replacement = CalendarEvent(
+            calendar_id=event.calendar_id,
+            uid=rep_uid,
+            summary=r.get('summary', event.summary),
+            description=r.get('description', event.description),
+            location=r.get('location', event.location),
+            dtstart=rep_start,
+            dtend=rep_end,
+            all_day=r.get('all_day', event.all_day),
+            recurrence_rule=None,
+            ical_data='',
+        )
+        replacement.ical_data = _build_ical(
+            rep_uid, replacement.summary, rep_start, rep_end,
+            replacement.all_day, replacement.description or '',
+            replacement.location or '', '',
+        )
+        db.session.add(replacement)
+
+    event.ical_data = _build_ical(
+        event.uid, event.summary, event.dtstart, event.dtend,
+        event.all_day, event.description or '', event.location or '',
+        event.recurrence_rule or '',
+        event.exdates.split(',') if event.exdates else None,
+    )
+    event.updated_at = datetime.now(timezone.utc)
+    db.session.commit()
+    return jsonify({
+        'event': event.to_dict(),
+        'replacement': replacement.to_dict() if replacement else None,
+    }), 200
+
+
 @api_bp.route('/events/<int:event_id>', methods=['DELETE'])
 @token_required
 def delete_event(event_id):
@@ -423,7 +497,7 @@ def _format_dt(dt, all_day=False):
     return dt.strftime('%Y%m%dT%H%M%SZ')
 
 
-def _build_vevent(uid, summary, dtstart, dtend, all_day, description='', location='', rrule=''):
+def _build_vevent(uid, summary, dtstart, dtend, all_day, description='', location='', rrule='', exdates=None):
     if not dtend:
         dtend = dtstart
     lines = [
@@ -443,10 +517,21 @@ def _build_vevent(uid, summary, dtstart, dtend, all_day, description='', locatio
         lines.append(f'LOCATION:{location}')
     if rrule:
         lines.append(f'RRULE:{rrule}')
+    if exdates:
+        for ex in exdates:
+            if all_day:
+                lines.append(f'EXDATE;VALUE=DATE:{ex.replace("-", "")}')
+            else:
+                # Convert ISO datetime (with or without TZ) into YYYYMMDDTHHMMSSZ
+                try:
+                    dt = datetime.fromisoformat(ex.replace('Z', '+00:00'))
+                    lines.append(f'EXDATE:{dt.strftime("%Y%m%dT%H%M%SZ")}')
+                except ValueError:
+                    pass
     lines.append(f'DTSTAMP:{datetime.now(timezone.utc).strftime("%Y%m%dT%H%M%SZ")}')
     lines.append('END:VEVENT')
     return '\r\n'.join(lines)
 
 
-def _build_ical(uid, summary, dtstart, dtend, all_day, description='', location='', rrule=''):
+def _build_ical(uid, summary, dtstart, dtend, all_day, description='', location='', rrule='', exdates=None):
-    return _build_vevent(uid, summary, dtstart, dtend, all_day, description, location, rrule)
+    return _build_vevent(uid, summary, dtstart, dtend, all_day, description, location, rrule, exdates)

backend/app/models/calendar.py

@@ -49,6 +49,7 @@ class CalendarEvent(db.Model):
     dtend = db.Column(db.DateTime, nullable=True)
     all_day = db.Column(db.Boolean, default=False)
     recurrence_rule = db.Column(db.Text, nullable=True)
+    exdates = db.Column(db.Text, nullable=True)  # Komma-separiert, ISO-Datum (YYYY-MM-DD)
     created_at = db.Column(db.DateTime, default=lambda: datetime.now(timezone.utc))
     updated_at = db.Column(db.DateTime, default=lambda: datetime.now(timezone.utc),
                            onupdate=lambda: datetime.now(timezone.utc))
@@ -65,6 +66,7 @@ class CalendarEvent(db.Model):
             'dtend': self.dtend.isoformat() if self.dtend else None,
             'all_day': self.all_day,
             'recurrence_rule': self.recurrence_rule,
+            'exdates': self.exdates.split(',') if self.exdates else [],
             'created_at': self.created_at.isoformat() if self.created_at else None,
             'updated_at': self.updated_at.isoformat() if self.updated_at else None,
         }

frontend/src/views/CalendarView.vue

@@ -186,6 +186,16 @@
       </template>
     </Dialog>
 
+    <!-- Scope picker for recurring events -->
+    <Dialog v-model:visible="showScopeDialog" header="Serientermin bearbeiten" modal :style="{ width: '440px' }">
+      <p>Dieser Termin gehoert zu einer Serie.<br>Was moechtest du bearbeiten?</p>
+      <template #footer>
+        <Button label="Abbrechen" text @click="showScopeDialog = false" />
+        <Button label="Nur diesen Termin" outlined @click="openEditScope('occurrence')" />
+        <Button label="Ganze Serie" @click="openEditScope('series')" />
+      </template>
+    </Dialog>
+
     <Dialog v-model:visible="confirmDeleteCal" header="Kalender loeschen" modal :style="{ width: '400px' }">
       <p>Moechtest du den Kalender <strong>{{ selectedCal?.name }}</strong> mit allen Terminen loeschen?</p>
       <template #footer>
@@ -271,6 +281,11 @@ const sharePermission = ref('read')
 const icalPassword = ref('')
 const confirmDeleteEvent = ref(false)
 const confirmDeleteCal = ref(false)
+const showScopeDialog = ref(false)
+const pendingScopeEvent = ref(null)
+const pendingScopeOccurrence = ref(null)
+// 'series' (edit master), 'occurrence' (split off single date), or null (non-recurring)
+const currentEditScope = ref(null)
 const permOptions = [{ label: 'Lesen', value: 'read' }, { label: 'Lesen+Schreiben', value: 'readwrite' }]
 
 const ownCalendars = computed(() => calendars.value.filter(c => c.permission === 'owner'))
@@ -354,12 +369,14 @@ function toFcEvent(e, cal) {
     extendedProps: { ...e, _cal: cal },
   }
   if (e.recurrence_rule) {
-    // FullCalendar rrule plugin consumes the RRULE together with dtstart
     fc.rrule = {
       freq: extractFreq(e.recurrence_rule),
       dtstart: e.dtstart,
       ...parseRRule(e.recurrence_rule),
     }
+    if (e.exdates && e.exdates.length) {
+      fc.exdate = e.exdates
+    }
     if (e.dtend && e.dtstart) {
       const ms = new Date(e.dtend).getTime() - new Date(e.dtstart).getTime()
       if (ms > 0) fc.duration = msToDuration(ms)
@@ -443,9 +460,47 @@ function loadRRuleIntoForm(rrule) {
 
 function onEventClick(info) {
   const e = info.event.extendedProps
+  if (e.recurrence_rule) {
+    pendingScopeEvent.value = e
+    pendingScopeOccurrence.value = info.event.start
+    showScopeDialog.value = true
+    return
+  }
+  currentEditScope.value = null
   openEditEvent(e)
 }
 
+function openEditScope(scope) {
+  showScopeDialog.value = false
+  const e = pendingScopeEvent.value
+  const occ = pendingScopeOccurrence.value
+  if (scope === 'series') {
+    currentEditScope.value = 'series'
+    openEditEvent(e)
+  } else {
+    // "Nur diesen Termin" - form starts from the clicked occurrence's
+    // start/end, non-recurring. Save will add an EXDATE on the master
+    // plus create a standalone event.
+    currentEditScope.value = 'occurrence'
+    editingEvent.value = e
+    const durationMs = e.dtend ? new Date(e.dtend) - new Date(e.dtstart) : 3600000
+    const occEnd = new Date(occ.getTime() + durationMs)
+    eventForm.value = {
+      summary: e.summary,
+      description: e.description || '',
+      location: e.location || '',
+      calendar_id: e.calendar_id,
+      dtstart: toLocalISO(occ, e.all_day),
+      dtend: toLocalISO(occEnd, e.all_day),
+      all_day: e.all_day,
+    }
+    loadRRuleIntoForm('')
+    // Freeze recurrence editor - this is a single instance
+    recurFreq.value = 'none'
+    showEventDialog.value = true
+  }
+}
+
 function onDateSelect(info) {
   openNewEvent(info.start, info.end, info.allDay)
 }
@@ -534,12 +589,28 @@ async function saveEvent() {
     calendar_id: eventForm.value.calendar_id,
   }
   try {
-    if (editingEvent.value) {
+    if (currentEditScope.value === 'occurrence' && editingEvent.value) {
+      // Split single occurrence off the series: add EXDATE + create replacement
+      await apiClient.post(`/events/${editingEvent.value.id}/exception`, {
+        occurrence_date: toLocalISO(pendingScopeOccurrence.value, editingEvent.value.all_day),
+        replacement: {
+          summary: payload.summary,
+          description: payload.description,
+          location: payload.location,
+          dtstart: payload.dtstart,
+          dtend: payload.dtend,
+          all_day: payload.all_day,
+        },
+      })
+    } else if (editingEvent.value) {
       await apiClient.put(`/events/${editingEvent.value.id}`, payload)
     } else {
       await apiClient.post(`/calendars/${payload.calendar_id}/events`, payload)
     }
     showEventDialog.value = false
+    currentEditScope.value = null
+    pendingScopeEvent.value = null
+    pendingScopeOccurrence.value = null
     refreshEvents()
   } catch (err) {
     toast.add({ severity: 'error', summary: 'Fehler', detail: err.response?.data?.error, life: 5000 })