fix: resolve all 12 TypeScript errors (tsc --noEmit clean)

- mail.ts: add explicit types to decodeMimeHeader callback params
- SessionList.tsx: use React.MouseEvent instead of nativeEvent
- ComposeModal.tsx: construct name from first_name + last_name
- MailDetail.tsx: destructure onReply/onForward from props
- RichTextEditor.tsx: use SetContentOptions object instead of boolean
- MailSearchBar.tsx: add optional value prop to interface
- EmptyState.tsx: add optional children prop
- Badge.tsx: add secondary variant to BadgeVariant, variantClasses, dotColors
- ConfirmDialog.tsx: add optional children prop
- hooks.ts: extend SearchResult type to include mail/file/event

frontend/src/components/ui/Badge.tsx

@@ -1,7 +1,7 @@
 import React from 'react';
 import clsx from 'clsx';
 
-export type BadgeVariant = 'default' | 'primary' | 'success' | 'warning' | 'danger' | 'info';
+export type BadgeVariant = 'default' | 'primary' | 'success' | 'warning' | 'danger' | 'info' | 'secondary';
 
 export interface BadgeProps {
   variant?: BadgeVariant;
@@ -17,6 +17,7 @@ const variantClasses: Record<BadgeVariant, string> = {
   warning: 'bg-warning-100 text-warning-700',
   danger: 'bg-danger-100 text-danger-700',
   info: 'bg-accent-100 text-accent-700',
+  secondary: 'bg-secondary-200 text-secondary-800',
 };
 
 const dotColors: Record<BadgeVariant, string> = {
@@ -26,6 +27,7 @@ const dotColors: Record<BadgeVariant, string> = {
   warning: 'bg-warning-500',
   danger: 'bg-danger-500',
   info: 'bg-accent-500',
+  secondary: 'bg-secondary-500',
 };
 
 export function Badge({ variant = 'default', children, className, dot = false }: BadgeProps) {