feat: add email forwarding message channel (#19535)

## Summary

- Add email forwarding as a new message channel type, allowing users to
forward emails from addresses like `support@mycompany.com` into Twenty
- Inbound emails arrive via S3 (SES → S3 bucket), are polled by a cron
job, parsed, routed to the correct workspace/channel, and persisted as
messages
- Dedicated settings page at `/settings/accounts/new-email-forwarding`
where users provide their source email handle and receive a unique
forwarding address
- Forwarding channels bypass the IMAP/mailbox sync state machine — they
skip cron-driven sync, relaunch, and message-list-fetch lifecycle stages
- Forwarding address section shown at the top of the Emails settings
page so users can find/copy their addresses after initial setup
- Tab names for forwarding channels display the user-provided handle
(e.g. `support@mycompany.com`) instead of the internal routing address
- Shared utilities extracted from IMAP driver: `extractThreadId`,
`extractParticipants`, `extractAddresses` to avoid code duplication
- Uses the existing S3 bucket (STORAGE_S3_*) with `inbound-email/`
prefix — no separate bucket needed
- Feature gated behind `isEmailForwardingEnabled` client config
(requires `INBOUND_EMAIL_DOMAIN` + S3 storage)

## New backend modules

- `InboundEmailS3ClientProvider` — lazy-initialized S3 client using
existing storage config
- `InboundEmailStorageService` — S3 operations (get, move to
processed/unmatched/failed)
- `InboundEmailParserService` — RFC 822 parsing via `postal-mime`,
builds `MessageWithParticipants`
- `InboundEmailImportService` — orchestrates download → parse → route →
persist → archive
- `MessagingInboundEmailPollCronJob` — polls S3 `incoming/` prefix,
enqueues import jobs
- `CreateEmailForwardingChannelInput` DTO — accepts user-provided
`handle`

## New frontend components

- `SettingsAccountsNewEmailForwardingChannel` — dedicated page with
handle input form + forwarding address result
- `SettingsAccountsEmailForwardingSection` — forwarding address list on
the Emails settings page
- `useConnectedAccountHandleMap` — shared hook for account ID → handle
lookup
- `useCreateEmailForwardingChannel` — mutation hook accepting handle
parameter

## Test plan

- [x] 17 unit tests for inbound email import service (all outcomes:
imported, unmatched, loop_dropped, unconfigured, parse_failed,
persist_failed)
- [x] 16 tests for `computeSyncStatus` including EMAIL_FORWARDING cases
- [x] 11 tests for `extractEnvelopeRecipient` utility
- [x] TypeScript typechecks pass for both twenty-server and twenty-front
- [x] Lint passes for both packages
- [ ] Manual: create forwarding channel, verify forwarding address
generated
- [ ] Manual: send email to forwarding address, verify it appears in
Twenty

https://claude.ai/code/session_01KpyF6p4cUEnuaT4h8DP5Pm

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>
Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: neo773 <62795688+neo773@users.noreply.github.com>
Co-authored-by: neo773 <neo773@protonmail.com>

packages/twenty-front/src/modules/client-config/hooks/useClientConfig.ts

@@ -13,12 +13,13 @@ import { isDeveloperDefaultSignInPrefilledState } from '@/client-config/states/i
 import { isClickHouseConfiguredState } from '@/client-config/states/isClickHouseConfiguredState';
 import { isCloudflareIntegrationEnabledState } from '@/client-config/states/isCloudflareIntegrationEnabledState';
 import { isDDLLockedState } from '@/client-config/states/isDDLLockedState';
-import { maintenanceModeState } from '@/client-config/states/maintenanceModeState';
+import { isEmailGroupEnabledState } from '@/client-config/states/isEmailGroupEnabledState';
 import { isEmailingDomainsEnabledState } from '@/client-config/states/isEmailingDomainsEnabledState';
 import { isEmailVerificationRequiredState } from '@/client-config/states/isEmailVerificationRequiredState';
 import { isGoogleCalendarEnabledState } from '@/client-config/states/isGoogleCalendarEnabledState';
 import { isGoogleMessagingEnabledState } from '@/client-config/states/isGoogleMessagingEnabledState';
 import { isImapSmtpCaldavEnabledState } from '@/client-config/states/isImapSmtpCaldavEnabledState';
+import { maintenanceModeState } from '@/client-config/states/maintenanceModeState';
 import { isMicrosoftCalendarEnabledState } from '@/client-config/states/isMicrosoftCalendarEnabledState';
 import { isMicrosoftMessagingEnabledState } from '@/client-config/states/isMicrosoftMessagingEnabledState';
 import { isMultiWorkspaceEnabledState } from '@/client-config/states/isMultiWorkspaceEnabledState';
@@ -100,13 +101,16 @@ export const useClientConfig = (): UseClientConfigResult => {
 
   const setCalendarBookingPageId = useSetAtomState(calendarBookingPageIdState);
 
-  const setIsImapSmtpCaldavEnabled = useSetAtomState(
-    isImapSmtpCaldavEnabledState,
-  );
+  const setIsEmailGroupEnabled = useSetAtomState(isEmailGroupEnabledState);
+
   const setIsEmailingDomainsEnabled = useSetAtomState(
     isEmailingDomainsEnabledState,
   );
 
+  const setIsImapSmtpCaldavEnabled = useSetAtomState(
+    isImapSmtpCaldavEnabledState,
+  );
+
   const setAllowRequestsToTwentyIcons = useSetAtomState(
     allowRequestsToTwentyIconsState,
   );
@@ -195,6 +199,7 @@ export const useClientConfig = (): UseClientConfigResult => {
 
       setCalendarBookingPageId(clientConfig?.calendarBookingPageId ?? null);
       setIsImapSmtpCaldavEnabled(clientConfig?.isImapSmtpCaldavEnabled);
+      setIsEmailGroupEnabled(clientConfig?.isEmailGroupEnabled ?? false);
       setIsEmailingDomainsEnabled(clientConfig?.isEmailingDomainsEnabled);
       setAllowRequestsToTwentyIcons(clientConfig?.allowRequestsToTwentyIcons);
       setIsCloudflareIntegrationEnabled(
@@ -233,6 +238,7 @@ export const useClientConfig = (): UseClientConfigResult => {
     setIsDeveloperDefaultSignInPrefilled,
     setIsEmailVerificationRequired,
     setIsImapSmtpCaldavEnabled,
+    setIsEmailGroupEnabled,
     setIsMultiWorkspaceEnabled,
     setIsEmailingDomainsEnabled,
     setIsClickHouseConfigured,