Keep synced messages and events when removing a workspace member (#21443)

## Context

Removing a workspace member deletes their connected accounts, which
cascades into deleting every message and calendar event those accounts
synced. For a CRM, losing the email history of departed teammates is a
big deal.

## What this does

Connected accounts are now kept and reassigned instead of deleted when a
member is removed:

- Ownership moves to the acting user (whoever removed the member). When
members remove themselves (leave workspace, account deletion), it falls
back to the oldest admin.
- OAuth tokens are revoked, credentials wiped, message/calendar channels
get `isSyncEnabled = false`, and the account is stamped with a new
`archivedAt` column (fast instance command included).
- Synced messages, threads and calendar events stay in the workspace.
Channel visibility settings keep applying as before, since channels and
associations survive.
- The reassigned account appears in the new owner's Settings → Accounts,
where it can still be deleted (with its data) like any other account.

The transfer happens synchronously during removal, while the member's
userWorkspace row still exists. This also removes
`DeleteWorkspaceMemberConnectedAccountsCleanupJob` and its listener: the
async job had to reconstruct the account-owner link from rows the
removal flow had just deleted, which was race-prone (see 2181fb541e).

Archived accounts are excluded from the workflow send-email default
account resolution, and both removal confirmation modals now mention
what happens to synced data.

---------

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>

packages/twenty-server/src/engine/core-modules/tool/tools/email-tool/email-composer.service.ts

@@ -11,7 +11,7 @@ import {
   FileFolder,
 } from 'twenty-shared/types';
 import { isDefined, isValidUuid } from 'twenty-shared/utils';
-import { In, LessThanOrEqual, type Repository } from 'typeorm';
+import { In, IsNull, LessThanOrEqual, type Repository } from 'typeorm';
 import { z } from 'zod';
 
 import { FileEntity } from 'src/engine/core-modules/file/entities/file.entity';
@@ -97,7 +97,7 @@ export class EmailComposerService {
     return this.globalWorkspaceOrmManager.executeInWorkspaceContext(
       async () => {
         const allAccounts = await this.connectedAccountRepository.find({
-          where: { workspaceId },
+          where: { workspaceId, archivedAt: IsNull() },
         });
 
         if (!allAccounts || allAccounts.length === 0) {