feat: P2.3 Folder Sharing + P2.5 Email Import + P2.6 Contact Import + P2.7 Free/Busy

- P2.3: Folder sharing system — ShareFolderDialog, sharing-store, sharing-settings
- P2.5: Email import (.eml, .tgz, .zip) with dedup and progress
- P2.6: Contact import (vCard + CSV) with auto-mapping
- P2.7: Free/Busy view grid with color-coded slots

components/layout/mailbox-context-menu.tsx

@@ -21,6 +21,7 @@ import {
   FolderX,
   RefreshCw,
   Upload,
+  Share2,
 } from "lucide-react";
 
 interface Position {
@@ -86,6 +87,7 @@ interface MailboxContextMenuProps {
   onRenameFolder?: (mailboxId: string) => void;
   onDeleteFolder?: (mailboxId: string) => void;
   onImportEmail?: (mailboxId: string) => void;
+  onShareFolder?: (mailboxId: string) => void;
   onRefresh?: () => void;
 }
 
@@ -105,6 +107,7 @@ export function MailboxContextMenu({
   onRenameFolder,
   onDeleteFolder,
   onImportEmail,
+  onShareFolder,
   onRefresh,
 }: MailboxContextMenuProps) {
   const t = useTranslations("mailbox_context_menu");
@@ -191,6 +194,12 @@ export function MailboxContextMenu({
         onClick={() => handleAction(() => onRenameFolder?.(mailbox.id))}
         disabled={!onRenameFolder || !canRename}
       />
+      <ContextMenuItem
+        icon={Share2}
+        label={t("share_folder")}
+        onClick={() => handleAction(() => onShareFolder?.(mailbox.id))}
+        disabled={!onShareFolder || mailbox.isShared}
+      />
 
       <ContextMenuSeparator />
 

components/layout/sidebar.tsx

@@ -90,6 +90,7 @@ interface SidebarProps {
   onDeleteFolder?: (mailboxId: string) => void;
   onImportEmail?: (mailboxId: string) => void;
   onRefreshMailboxes?: () => void;
+  onShareFolder?: (mailboxId: string) => void;
   scheduledTotal?: number;
   showScheduledMailbox?: boolean;
   /** True when the unified view spans multiple login accounts (cross-account).
@@ -779,6 +780,7 @@ export function Sidebar({
   onDeleteFolder,
   onImportEmail,
   onRefreshMailboxes,
+  onShareFolder,
   scheduledTotal = 0,
   showScheduledMailbox = false,
   crossAccountActive = false,
@@ -1452,6 +1454,7 @@ export function Sidebar({
         onRenameFolder={onRenameFolder}
         onDeleteFolder={onDeleteFolder}
         onImportEmail={onImportEmail}
+        onShareFolder={onShareFolder}
         onRefresh={onRefreshMailboxes}
       />
     </div>