fix(server): avoid job fail if mail is not configured (#12306)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Improved email notification handling to prevent errors from interrupting other processes when sending emails is not possible.
- **Refactor**
  - Updated internal email sending logic across notifications and workspace features for more robust operation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/__tests__/mocks/mailer.mock.ts

@@ -6,6 +6,9 @@ import { MailName } from '../../mails';
 
 export class MockMailer {
   send = Sinon.createStubInstance(Mailer).send.resolves(true);
+  trySend(command: Jobs['notification.sendMail']) {
+    return this.send(command, true);
+  }
 
   last<Mail extends MailName>(
     name: Mail