Несколько ящиков у одного логина, общие ящики, кто ответил, вход ящик*логин

- V7: users.is_shared, mailbox_access (MEMBER от админа/Jambotron, ATTACHED по паролю ящика), messages.answered_by
- /api/mailboxes: мои ящики с непрочитанными, сессия другого ящика (JWT с claim by), подключить по паролю
  (LoginGuard), убрать из меню
- общий ящик: без своего входа (веб/SMTP/IMAP), участники открывают; «прочитано» общее; ответ из веба → answered_by
- SMTP/IMAP: ящик*логин + пароль логина (как master user в Dovecot)
- открытый чужой ящик (общий, подключённый, OPEN админа): профиль и пароль не меняются (403)
- админ: создать shared, участники ящика (PUT /{id}/members); служебное API: PUT /shared/{address};
  выключение аккаунта убирает и из общих ящиков
- UI: MAILBOXES в левом меню (переключение, ⊕ подключить, × убрать), shared/участники в настройках,
  «Answered by» у письма
- 88 тестов; живой прогон на Postgres 17 (апгрейд V6→V7 на данных), скриншоты UI

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/app/core/api.service.ts

@@ -1,7 +1,7 @@
 import { Injectable, inject } from '@angular/core';
 import { HttpClient } from '@angular/common/http';
 import { Observable } from 'rxjs';
-import { Attachment, BlacklistEntry, Contact, Draft, Folder, MailList, Mailbox, MailboxCreated, Message, Profile, ServerConfig } from './models';
+import { Attachment, BlacklistEntry, Contact, Draft, Folder, MailList, Mailbox, MailboxCreated, MailboxEntry, Message, Profile, ServerConfig } from './models';
 
 /** The mail server REST API (same origin, /api). */
 @Injectable({ providedIn: 'root' })
@@ -19,8 +19,22 @@ export class ApiService {
 
   // mailboxes — administrators only
   mailboxes(): Observable<Mailbox[]> { return this.http.get<Mailbox[]>('/api/admin/mailboxes'); }
-  createMailbox(email: string, displayName: string, password: string): Observable<MailboxCreated> {
-    return this.http.post<MailboxCreated>('/api/admin/mailboxes', { email, displayName, password });
+  createMailbox(email: string, displayName: string, password: string, shared = false): Observable<MailboxCreated> {
+    return this.http.post<MailboxCreated>('/api/admin/mailboxes', { email, displayName, password, shared });
+  }
+  setMailboxMembers(id: number, members: string[]): Observable<Mailbox> {
+    return this.http.put<Mailbox>(`/api/admin/mailboxes/${id}/members`, { members });
+  }
+  // the logged-in user's mailboxes (left menu)
+  myMailboxes(): Observable<MailboxEntry[]> { return this.http.get<MailboxEntry[]>('/api/mailboxes'); }
+  mailboxSession(email: string): Observable<{ token: string; email: string }> {
+    return this.http.post<{ token: string; email: string }>(`/api/mailboxes/${encodeURIComponent(email)}/session`, {});
+  }
+  attachMailbox(email: string, password: string): Observable<MailboxEntry> {
+    return this.http.post<MailboxEntry>('/api/mailboxes/attach', { email, password });
+  }
+  leaveMailbox(email: string): Observable<void> {
+    return this.http.delete<void>(`/api/mailboxes/${encodeURIComponent(email)}`);
   }
   newMailboxPassword(id: number): Observable<MailboxCreated> {
     return this.http.post<MailboxCreated>(`/api/admin/mailboxes/${id}/password`, {});
@@ -67,8 +81,8 @@ export class ApiService {
   // compose
   createDraft(draft: Draft): Observable<Message> { return this.http.post<Message>('/api/drafts', draft); }
   updateDraft(id: number, draft: Draft): Observable<Message> { return this.http.put<Message>(`/api/drafts/${id}`, draft); }
-  send(draft: Draft, draftId: number | null): Observable<Message> {
-    return this.http.post<Message>('/api/send', { ...draft, draftId });
+  send(draft: Draft, draftId: number | null, replyToId: number | null = null): Observable<Message> {
+    return this.http.post<Message>('/api/send', { ...draft, draftId, replyToId });
   }
 
   // attachments

frontend/src/app/core/auth.service.ts

@@ -40,6 +40,18 @@ export class AuthService {
     this.openedBy.set(read('adminEmail'));
   }
 
+  /**
+   * Switch to another mailbox of the same login (left menu). Going back to the mailbox an administrator came
+   * from ends the administrator's visit.
+   */
+  switchTo(response: TokenResponse): void {
+    if (this.openedBy() && response.email === this.openedBy()) {
+      this.backToAdmin();
+      return;
+    }
+    this.store(response);
+  }
+
   /** Back to the administrator's own mailbox. */
   backToAdmin(): void {
     const token = read('adminToken');

frontend/src/app/core/models.ts

@@ -23,6 +23,16 @@ export interface Message {
   receivedAt: string;
   hasAttachments: boolean;
   attachmentCount: number;
+  answeredBy?: string | null;   // login that answered it from the web client (shared mailboxes)
+}
+
+/** MailboxAccess.Entry — a mailbox of the logged-in user (left menu) */
+export interface MailboxEntry {
+  email: string;
+  displayName: string;
+  kind: 'OWN' | 'MEMBER' | 'ATTACHED';
+  shared: boolean;
+  unread: number;
 }
 
 export interface Attachment {
@@ -63,7 +73,9 @@ export interface Mailbox {
   displayName: string;
   active: boolean;
   admin: boolean;
-  trap: boolean;          // what it sends stays in its own INBOX, nothing leaves the server (staging@)
+  trap: boolean;          // what it sends to outside addresses stays in its own INBOX (staging@)
+  shared: boolean;        // shared mailbox: no login of its own, members open it
+  members: string[];      // who may open it
   usedBytes: number;
   quotaBytes: number;
   createdAt: string;