Fix member removal bug + QA fixes + shared calendar sidebar styling

Bug fix:
- CalendarMemberRow: add type="button" to remove button (was submitting parent form)

QA fixes:
- EventDetailPanel: use axios.isAxiosError() instead of duck-typing for lock errors
- EventDetailPanel: only call onSaved on create (edits return to view mode, not close)
- CalendarForm: remove 4 redundant membersQuery.refetch() calls (mutations already invalidate)
- useEventLock: remove unused lockHeld ref from return, fix stale eventId in onSuccess
- EventLockBanner: guard against invalid date parse

UI:
- SharedCalendarSection: add purple Ghost icon next to "SHARED CALENDARS" header

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

frontend/src/components/calendar/CalendarForm.tsx

@@ -101,25 +101,21 @@ export default function CalendarForm({ calendar, onClose }: CalendarFormProps) {
       permission: 'read_only',
       canAddOthers: false,
     });
-    membersQuery.refetch();
   };
 
   const handleUpdatePermission = async (memberId: number, permission: CalendarPermission) => {
     if (!calendar) return;
     await updateMember({ calendarId: calendar.id, memberId, permission });
-    membersQuery.refetch();
   };
 
   const handleUpdateCanAddOthers = async (memberId: number, canAddOthers: boolean) => {
     if (!calendar) return;
     await updateMember({ calendarId: calendar.id, memberId, canAddOthers });
-    membersQuery.refetch();
   };
 
   const handleRemoveMember = async (memberId: number) => {
     if (!calendar) return;
     await removeMember({ calendarId: calendar.id, memberId });
-    membersQuery.refetch();
   };
 
   const canDelete = calendar && !calendar.is_default && !calendar.is_system;

frontend/src/components/calendar/CalendarMemberRow.tsx

@@ -79,6 +79,7 @@ export default function CalendarMemberRow({
           )}
 
           <button
+            type="button"
             onClick={handleRemoveClick}
             className="text-muted-foreground hover:text-destructive transition-colors"
             title={confirming ? 'Click again to confirm' : 'Remove member'}

frontend/src/components/calendar/EventDetailPanel.tsx

@@ -5,6 +5,7 @@ import { format, parseISO } from 'date-fns';
 import {
   X, Pencil, Trash2, Save, Clock, MapPin, AlignLeft, Repeat, Star, Calendar, Loader2,
 } from 'lucide-react';
+import axios from 'axios';
 import api, { getErrorMessage } from '@/lib/api';
 import type { CalendarEvent, Location as LocationType, RecurrenceRule, CalendarPermission, EventLockInfo } from '@/types';
 import { useCalendars } from '@/hooks/useCalendars';
@@ -328,11 +329,11 @@ export default function EventDetailPanel({
       toast.success(isCreating ? 'Event created' : 'Event updated');
       if (isCreating) {
         onClose();
+        onSaved?.();
       } else {
         setIsEditing(false);
         setEditScope(null);
       }
-      onSaved?.();
     },
     onError: (error) => {
       toast.error(getErrorMessage(error, isCreating ? 'Failed to create event' : 'Failed to update event'));
@@ -367,18 +368,16 @@ export default function EventDetailPanel({
         await acquireLock();
         setLockInfo(null);
       } catch (err: unknown) {
-        if (err && typeof err === 'object' && 'response' in err) {
-          const axErr = err as { response?: { status?: number; data?: { detail?: string; locked_by_name?: string; expires_at?: string; is_permanent?: boolean } } };
-          if (axErr.response?.status === 423) {
+        if (axios.isAxiosError(err) && err.response?.status === 423) {
+          const data = err.response.data as { locked_by_name?: string; expires_at?: string; is_permanent?: boolean } | undefined;
           setLockInfo({
             locked: true,
-              locked_by_name: axErr.response.data?.locked_by_name || 'another user',
-              expires_at: axErr.response.data?.expires_at || null,
-              is_permanent: axErr.response.data?.is_permanent || false,
+            locked_by_name: data?.locked_by_name || 'another user',
+            expires_at: data?.expires_at || null,
+            is_permanent: data?.is_permanent || false,
           });
           return;
         }
-        }
         toast.error('Failed to acquire edit lock');
         return;
       }

frontend/src/components/calendar/EventLockBanner.tsx

@@ -20,7 +20,7 @@ export default function EventLockBanner({ lockedByName, expiresAt, isPermanent =
           </p>
           {!isPermanent && expiresAt && (
             <p className="text-xs text-muted-foreground">
-              Lock expires at {format(parseISO(expiresAt), 'h:mm a')}
+              Lock expires at {(() => { try { return format(parseISO(expiresAt), 'h:mm a'); } catch { return 'unknown'; } })()}
             </p>
           )}
         </div>

frontend/src/components/calendar/SharedCalendarSection.tsx

@@ -1,5 +1,5 @@
 import { useState } from 'react';
-import { Pencil } from 'lucide-react';
+import { Ghost, Pencil } from 'lucide-react';
 import { Checkbox } from '@/components/ui/checkbox';
 import type { SharedCalendarMembership } from '@/types';
 import SharedCalendarSettings from './SharedCalendarSettings';
@@ -36,7 +36,8 @@ export default function SharedCalendarSection({
   return (
     <>
       <div className="space-y-1.5">
-        <div className="px-2">
+        <div className="flex items-center gap-1.5 px-2">
+          <Ghost className="h-3.5 w-3.5 text-violet-400 shrink-0" />
           <span className="text-[11px] font-semibold uppercase tracking-wider text-muted-foreground">
             Shared Calendars
           </span>

frontend/src/hooks/useEventLock.ts

@@ -14,9 +14,9 @@ export function useEventLock(eventId: number | null) {
       );
       return data;
     },
-    onSuccess: () => {
+    onSuccess: (_data, lockedId) => {
       lockHeldRef.current = true;
-      activeEventIdRef.current = eventId;
+      activeEventIdRef.current = lockedId;
     },
   });
 
@@ -64,6 +64,5 @@ export function useEventLock(eventId: number | null) {
     release,
     isAcquiring: acquireMutation.isPending,
     acquireError: acquireMutation.error,
-    lockHeld: lockHeldRef.current,
   };
 }