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

lib/jmap/client-interface.ts

@@ -1,4 +1,4 @@
-import type { Email, Mailbox, StateChange, AccountStates, Thread, Identity, EmailAddress, ContactCard, AddressBook, AddressBookRights, VacationResponse, Calendar, CalendarRights, CalendarEvent, CalendarEventFilter, CalendarTask, FileNode, FileNodeRights, Principal, PushSubscription, ScheduledEmail, SendEmailResult, SharedAccount } from "./types";
+import type { Email, Mailbox, MailboxRights, StateChange, AccountStates, Thread, Identity, EmailAddress, ContactCard, AddressBook, AddressBookRights, VacationResponse, Calendar, CalendarRights, CalendarEvent, CalendarEventFilter, CalendarTask, FileNode, FileNodeRights, Principal, PushSubscription, ScheduledEmail, SendEmailResult, SharedAccount } from "./types";
 import type { SieveScript, SieveCapabilities } from "./sieve-types";
 
 /**
@@ -315,6 +315,7 @@ export interface IJMAPClient {
   setCalendarShare(calendarId: string, principalId: string, rights: CalendarRights | null, targetAccountId?: string): Promise<void>;
   setAddressBookShare(addressBookId: string, principalId: string, rights: AddressBookRights | null, targetAccountId?: string): Promise<void>;
   setFileNodeShare(fileNodeId: string, principalId: string, rights: FileNodeRights | null, targetAccountId?: string): Promise<void>;
+  setMailboxShare(mailboxId: string, principalId: string, rights: MailboxRights | null, targetAccountId?: string): Promise<void>;
 
   // ── Accounts (primary + shared/group) ────────────────────────
   getSharedAccounts(): SharedAccount[];

lib/jmap/client.ts

@@ -1,4 +1,4 @@
-import type { Email, Mailbox, StateChange, AccountStates, Thread, Identity, EmailAddress, ContactCard, AddressBook, AddressBookRights, VacationResponse, Calendar, CalendarRights, CalendarEvent, CalendarEventFilter, CalendarTask, FileNode, FileNodeFilter, FileNodeRights, Principal, PushSubscription, EmailSubmission, ScheduledEmail, SendEmailResult, SharedAccount } from "./types";
+import type { Email, Mailbox, MailboxRights, StateChange, AccountStates, Thread, Identity, EmailAddress, ContactCard, AddressBook, AddressBookRights, VacationResponse, Calendar, CalendarRights, CalendarEvent, CalendarEventFilter, CalendarTask, FileNode, FileNodeFilter, FileNodeRights, Principal, PushSubscription, EmailSubmission, ScheduledEmail, SendEmailResult, SharedAccount } from "./types";
 import type { SieveScript, SieveCapabilities } from "./sieve-types";
 import type { IJMAPClient } from "./client-interface";
 import { toWildcardQuery } from "./search-utils";
@@ -4426,6 +4426,34 @@ export class JMAPClient implements IJMAPClient {
     }
   }
 
+  /**
+   * Add, update, or remove a principal's rights on a mailbox folder.
+   * Pass `rights: null` to revoke access.
+   */
+  async setMailboxShare(
+    mailboxId: string,
+    principalId: string,
+    rights: MailboxRights | null,
+    targetAccountId?: string,
+  ): Promise<void> {
+    const accountId = targetAccountId || this.accountId;
+    const response = await this.request([
+      ["Mailbox/set", {
+        accountId,
+        update: { [mailboxId]: { [`shareWith/${principalId}`]: rights } },
+      }, "0"],
+    ]);
+
+    const result = response.methodResponses?.[0]?.[1];
+    if (result?.notUpdated?.[mailboxId]) {
+      const err = result.notUpdated[mailboxId];
+      throw new Error(err.description || "Failed to update mailbox share");
+    }
+    if (!result?.updated || !(mailboxId in result.updated)) {
+      throw new Error("Server did not confirm the share update");
+    }
+  }
+
   private async fetchPaginatedContacts(
     accountId: string,
     filter?: Record<string, unknown>,

lib/jmap/types.ts

@@ -181,6 +181,19 @@ export interface Attachment {
   disposition?: string;
 }
 
+export interface MailboxRights {
+  mayReadItems: boolean;
+  mayAddItems: boolean;
+  mayRemoveItems: boolean;
+  maySetSeen: boolean;
+  maySetKeywords: boolean;
+  mayCreateChild: boolean;
+  mayRename: boolean;
+  mayDelete: boolean;
+  maySubmit: boolean;
+  mayShare?: boolean;
+}
+
 export interface Mailbox {
   id: string;
   originalId?: string; // Original JMAP ID (for shared mailboxes)
@@ -192,22 +205,13 @@ export interface Mailbox {
   unreadEmails: number;
   totalThreads: number;
   unreadThreads: number;
-  myRights: {
-    mayReadItems: boolean;
-    mayAddItems: boolean;
-    mayRemoveItems: boolean;
-    maySetSeen: boolean;
-    maySetKeywords: boolean;
-    mayCreateChild: boolean;
-    mayRename: boolean;
-    mayDelete: boolean;
-    maySubmit: boolean;
-  };
+  myRights: MailboxRights;
   isSubscribed: boolean;
   // Shared folder support
   accountId?: string;
   accountName?: string;
   isShared?: boolean;
+  shareWith?: Record<string, MailboxRights> | null;
 }
 
 export interface Thread {