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/api/hooks.ts

@@ -67,7 +67,7 @@ export interface AuditLogEntry {
 }
 
 export interface SearchResult {
-  type: 'company' | 'contact';
+  type: 'company' | 'contact' | 'mail' | 'file' | 'event';
   id: string;
   name: string;
   description?: string;

frontend/src/api/mail.ts

@@ -417,7 +417,7 @@ export function decodeMimeHeader(value: string | undefined | null): string {
           return decodeURIComponent(escape(decoded));
         } else {
           // Q encoding: replace _ with space, then decode =XX hex sequences
-          const qDecoded = encoded.replace(/_/g, ' ').replace(/=([0-9A-F]{2})/gi, (_m, hex) => {
+          const qDecoded = encoded.replace(/_/g, ' ').replace(/=([0-9A-F]{2})/gi, (_m: string, hex: string) => {
             return String.fromCharCode(parseInt(hex, 16));
           });
           return decodeURIComponent(escape(qDecoded));