fix(calendar): EWS uses NTLM auth + edit form stays open after save

- Replace ews-javascript-api (Basic Auth only) with httpntlm for EWS connections
- testEwsConnection uses GetFolder SOAP via NTLM
- fetchViaEws uses FindItem CalendarView SOAP via NTLM
- Edit form no longer auto-closes on save — shows "Erfolgreich gespeichert" instead
- Test button in edit mode uses saved credentials via /sources/:id/test endpoint
- Add saveSuccess i18n key (de/en)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/components/settings/calendar-settings-panel.tsx

@@ -39,6 +39,7 @@ export function CalendarSettingsPanel() {
   const [isSaving, setIsSaving] = useState(false);
   const [saveError, setSaveError] = useState<string | null>(null);
   const [editSaveError, setEditSaveError] = useState<string | null>(null);
+  const [editSaveSuccess, setEditSaveSuccess] = useState(false);
   const [testResults, setTestResults] = useState<Record<string, 'success' | 'error' | 'testing'>>({});
 
   // Load sources on mount
@@ -234,9 +235,11 @@ export function CalendarSettingsPanel() {
               <button
                 type="button"
                 className="text-muted-foreground hover:text-foreground transition-colors"
-                onClick={() =>
-                  setEditingId(editingId === source.id ? null : source.id)
-                }
+                onClick={() => {
+                  setEditingId(editingId === source.id ? null : source.id);
+                  setEditSaveSuccess(false);
+                  setEditSaveError(null);
+                }}
                 aria-label={`Edit ${source.name}`}
               >
                 <svg
@@ -288,6 +291,9 @@ export function CalendarSettingsPanel() {
           {editSaveError && (
             <p className="mb-3 text-sm text-destructive">{editSaveError}</p>
           )}
+          {editSaveSuccess && (
+            <p className="mb-3 text-sm text-green-600 dark:text-green-400">{t('calendar.saveSuccess') || 'Gespeichert'}</p>
+          )}
           <h3 className="mb-3 text-sm font-semibold text-foreground">
             Edit Source
           </h3>
@@ -310,12 +316,13 @@ export function CalendarSettingsPanel() {
             onSave={async (payload) => {
               setIsSaving(true);
               setEditSaveError(null);
+              setEditSaveSuccess(false);
               try {
                 const updated = await updateSource(editingId, payload);
                 setSources((prev) =>
                   prev.map((s) => (s.id === editingId ? updated : s)),
                 );
-                setEditingId(null);
+                setEditSaveSuccess(true);
               } catch {
                 setEditSaveError(t('calendar.saveError') || 'Fehler beim Speichern');
               } finally {