Respect Gmail retry-after in messaging throttle (#17850)

Gmail 429/403 rate-limit responses include an explicit retry-after
timestamp, usually ~15 minutes out.

The exponential backoff starts at 1 minute, so the channel burns through
all 5 retry attempts before the window actually closes and gets marked
as permanently failed.

Adds throttleRetryAfter to the message channel and uses max(backoff,
retryAfter) in isThrottled().

packages/twenty-server/src/modules/messaging/common/services/message-channel-sync-status.service.ts

@@ -116,6 +116,7 @@ export class MessageChannelSyncStatusService {
         syncCursor: '',
         syncStageStartedAt: null,
         throttleFailureCount: 0,
+        throttleRetryAfter: null,
         pendingGroupEmailsAction: MessageChannelPendingGroupEmailsAction.NONE,
       });
 
@@ -225,6 +226,7 @@ export class MessageChannelSyncStatusService {
         syncStatus: MessageChannelSyncStatus.ACTIVE,
         syncStage: MessageChannelSyncStage.MESSAGE_LIST_FETCH_PENDING,
         throttleFailureCount: 0,
+        throttleRetryAfter: null,
         syncStageStartedAt: null,
         syncedAt: new Date().toISOString(),
       });
@@ -307,6 +309,7 @@ export class MessageChannelSyncStatusService {
       await messageChannelRepository.update(messageChannelIds, {
         syncStage: MessageChannelSyncStage.FAILED,
         syncStatus: syncStatus,
+        throttleRetryAfter: null,
       });
 
       const metricsKey =

packages/twenty-server/src/modules/messaging/common/standard-objects/message-channel.workspace-entity.ts

@@ -98,6 +98,7 @@ export class MessageChannelWorkspaceEntity extends BaseWorkspaceEntity {
   syncStage: MessageChannelSyncStage;
   syncStageStartedAt: string | null;
   throttleFailureCount: number;
+  throttleRetryAfter: string | null;
   connectedAccount: EntityRelation<ConnectedAccountWorkspaceEntity>;
   connectedAccountId: string;
   messageChannelMessageAssociations: EntityRelation<