Microsoft 404 on folder delta endpoint permanently fails email sync

https://sonarly.com/issue/8521?type=bug

When Microsoft Graph API returns HTTP 404 during message list fetch (e.g., deleted folder), the exception handler permanently marks the message channel as FAILED_UNKNOWN instead of retrying, breaking email sync for the affected user.

Fix: ## Fix

The `handleNotFoundException` method was permanently failing the message channel (`FAILED_UNKNOWN`) when a `NOT_FOUND` exception occurred during `MESSAGE_LIST_FETCH`. This was incorrect because Microsoft Graph API legitimately returns HTTP 404 for its folder delta endpoint when a mail folder is deleted, moved, or otherwise inaccessible — which the Microsoft driver maps to `MessageImportDriverExceptionCode.NOT_FOUND`.

The fix removes the special-case branch that treated `NOT_FOUND` during `MESSAGE_LIST_FETCH` as an impossible/fatal state, and instead routes all `NOT_FOUND` exceptions (regardless of sync step) to the retry path: `resetAndMarkAsMessagesListFetchPending`. This is consistent with:
- How `SYNC_CURSOR_ERROR` is handled (also resets and retries)
- The original intent before the Oct 2025 refactor (commit `cd4800eb86d`) introduced the permanent failure path

```typescript file=packages/twenty-server/src/modules/messaging/message-import-manager/services/messaging-import-exception-handler.service.ts lines=247-256
private async handleNotFoundException(
    syncStep: MessageImportSyncStep,
    messageChannel: Pick<MessageChannelWorkspaceEntity, 'id'>,
    workspaceId: string,
  ): Promise<void> {
    await this.messageChannelSyncStatusService.resetAndMarkAsMessagesListFetchPending(
      [messageChannel.id],
      workspaceId,
    );
  }
```

The old code for `MESSAGE_LIST_FETCH` (which created a "should never happen" Sentry error and called `markAsFailed`) is entirely removed. When the delta link becomes invalid (folder deleted/moved), the sync cursor resets and the channel queues for a fresh list fetch rather than being permanently broken.

packages/twenty-server/src/modules/messaging/message-import-manager/services/messaging-import-exception-handler.service.ts

@@ -249,31 +249,6 @@ export class MessageImportExceptionHandlerService {
     messageChannel: Pick<MessageChannelWorkspaceEntity, 'id'>,
     workspaceId: string,
   ): Promise<void> {
-    if (syncStep === MessageImportSyncStep.MESSAGE_LIST_FETCH) {
-      await this.messageChannelSyncStatusService.markAsFailed(
-        [messageChannel.id],
-        workspaceId,
-        MessageChannelSyncStatus.FAILED_UNKNOWN,
-      );
-
-      this.exceptionHandlerService.captureExceptions(
-        [
-          new Error(
-            'Not Found exception occurred while fetching message list, which should never happen',
-          ),
-        ],
-        {
-          additionalData: {
-            messageChannelId: messageChannel.id,
-            syncStep,
-          },
-          workspace: { id: workspaceId },
-        },
-      );
-
-      return;
-    }
-
     await this.messageChannelSyncStatusService.resetAndMarkAsMessagesListFetchPending(
       [messageChannel.id],
       workspaceId,