fix: resolve all 69 ESLint warnings across 40 files

- Remove unused imports (Mail, CalendarIcon, Plus, Circle, cn, Link,
  MessageCircle, User, Tag, FolderUp, useEffect, LogOut, GripVertical,
  Check, X, HoverActionsMode, HoverActionsCorner, asn1js, Convert, etc.)
- Prefix unused variables/params with underscore to satisfy no-unused-vars
- Add missing React hook dependencies (exhaustive-deps)
- Wrap handleNavigateUp in useCallback and selectedGroupMembers in useMemo
- Remove unused eslint-disable directives in jmap/client.ts
- Replace as any with typed casts in filter-store and smime-store tests
- Remove dead code (macOk assignment, unused now variable)

components/settings/calendar-management-settings.tsx

@@ -6,7 +6,7 @@ import { useCalendarStore } from '@/stores/calendar-store';
 import { useAuthStore } from '@/stores/auth-store';
 import { toast } from '@/stores/toast-store';
 import { SettingsSection } from './settings-section';
-import { Plus, Pencil, Trash2, Check, X, Calendar as CalendarIcon, Copy, Link, Upload, Globe, RefreshCw, Eraser } from 'lucide-react';
+import { Plus, Pencil, Trash2, Calendar as CalendarIcon, Copy, Link, Upload, Globe, RefreshCw, Eraser } from 'lucide-react';
 import { cn, formatDateTime } from '@/lib/utils';
 import { ICalImportModal } from '@/components/calendar/ical-import-modal';
 import { ICalSubscriptionModal } from '@/components/calendar/ical-subscription-modal';