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/files/file-browser.tsx

@@ -453,13 +453,13 @@ export function FileBrowser({
         })),
       ];
 
-  const handleNavigateUp = () => {
+  const handleNavigateUp = useCallback(() => {
     if (currentPath === '/') return;
     const segments = currentPath.split('/').filter(Boolean);
     segments.pop();
     const parentPath = segments.length === 0 ? '/' : '/' + segments.join('/');
     onNavigate(parentPath, null);
-  };
+  }, [currentPath, onNavigate]);
 
   const handleResourceClick = (resource: FileResource, e: React.MouseEvent) => {
     if (resource.isDirectory) {