feat: Kalender-Freigaben per Stift-Button bearbeiten

Analog zu den Datei-Freigaben: Stift neben der Muelltonne in der
Share-Liste macht die Zeile zur Inline-Edit-Zeile mit Permission-
Dropdown + Check/X. Speichern nutzt denselben POST /share-
Endpoint, der auch das initiale Teilen erledigt - er erkennt den
existierenden User und aktualisiert nur die Berechtigung.

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

frontend/src/views/CalendarView.vue

@@ -163,12 +163,22 @@
             <Button label="Teilen" size="small" @click="shareCalendar" />
           </div>
           <div v-if="calendarShares.length" class="existing-shares">
-            <div v-for="s in calendarShares" :key="s.id" class="share-perm-item">
+            <template v-for="s in calendarShares" :key="s.id">
-              <i class="pi pi-user"></i>
+              <div v-if="editingShareId !== s.id" class="share-perm-item">
-              <span>{{ s.username }}</span>
+                <i class="pi pi-user"></i>
-              <span class="perm-label">{{ s.permission === 'readwrite' ? 'Lesen+Schreiben' : 'Lesen' }}</span>
+                <span>{{ s.username }}</span>
-              <Button icon="pi pi-trash" text size="small" severity="danger" @click="removeShare(s.id)" />
+                <span class="perm-label">{{ s.permission === 'readwrite' ? 'Lesen+Schreiben' : 'Lesen' }}</span>
-            </div>
+                <Button icon="pi pi-pencil" text size="small" title="Bearbeiten" @click="startEditShare(s)" />
+                <Button icon="pi pi-trash" text size="small" severity="danger" title="Entfernen" @click="removeShare(s.id)" />
+              </div>
+              <div v-else class="share-perm-item editing">
+                <i class="pi pi-user"></i>
+                <span>{{ s.username }}</span>
+                <Select v-model="editSharePermission" :options="permOptions" optionLabel="label" optionValue="value" />
+                <Button icon="pi pi-check" text size="small" severity="success" title="Speichern" @click="saveEditShare(s)" />
+                <Button icon="pi pi-times" text size="small" title="Abbrechen" @click="editingShareId = null" />
+              </div>
+            </template>
           </div>
         </div>
 
@@ -300,6 +310,8 @@ const shareUsername = ref('')
 const sharePermission = ref('read')
 const shareSearchResults = ref([])
 const calendarShares = ref([])
+const editingShareId = ref(null)
+const editSharePermission = ref('read')
 let shareSearchTimer = null
 const icalPassword = ref('')
 const confirmDeleteEvent = ref(false)
@@ -706,6 +718,26 @@ async function loadShares() {
   } catch { calendarShares.value = [] }
 }
 
+function startEditShare(s) {
+  editingShareId.value = s.id
+  editSharePermission.value = s.permission
+}
+
+async function saveEditShare(s) {
+  if (!selectedCal.value) return
+  try {
+    await apiClient.post(`/calendars/${selectedCal.value.id}/share`, {
+      username: s.username,
+      permission: editSharePermission.value,
+    })
+    editingShareId.value = null
+    await loadShares()
+    toast.add({ severity: 'success', summary: 'Berechtigung aktualisiert', life: 2500 })
+  } catch (err) {
+    toast.add({ severity: 'error', summary: 'Fehler', detail: err.response?.data?.error || err.message, life: 5000 })
+  }
+}
+
 async function removeShare(shareId) {
   if (!selectedCal.value) return
   try {
@@ -830,7 +862,8 @@ onMounted(async () => {
 .user-result { padding: 0.5rem 0.75rem; cursor: pointer; font-size: 0.875rem; display: flex; gap: 0.5rem; align-items: center; }
 .user-result:hover { background: var(--p-primary-50); }
 .existing-shares { margin-top: 0.5rem; }
-.share-perm-item { display: flex; align-items: center; gap: 0.5rem; padding: 0.375rem 0; font-size: 0.875rem; }
+.share-perm-item { display: flex; align-items: center; gap: 0.5rem; padding: 0.375rem 0; font-size: 0.875rem; flex-wrap: wrap; }
+.share-perm-item.editing { background: var(--p-surface-50); padding: 0.5rem; border-radius: 4px; }
 .perm-label { color: var(--p-text-muted-color); font-size: 0.75rem; }
 .ical-block { border-top: 1px solid var(--p-surface-200); padding-top: 1rem; margin-top: 1rem; }
 .ical-url { font-size: 0.8rem; display: flex; gap: 0.5rem; align-items: center; flex-wrap: wrap; }