fix: user invite email not sending and null variables

- Add missing BullModule queue registration and BullBoardModule to UsersModule
- Add invitingUser to event payloads to track who sent the invite
- Fix incorrect global variable in SendInviteUsersMailMessage (__views_dir -> __images_dirname)
- Use invitingUser as fromUser instead of invited user in email
- Update processors to use BullMQ pattern

Fixes issues:
1. Email not sending due to missing queue/processor registration
2. Null variables in email (firstName/lastName) because fromUser was the invited user
3. Image attachment failing due to wrong path

packages/server/src/modules/UsersModule/commands/SendInviteUsersMailMessage.service.ts

@@ -27,7 +27,7 @@ export class SendInviteUsersMailMessage {
     invite: ModelObject<UserInvite>,
   ) {
     const tenant = await this.tenancyContext.getTenant(true);
-    const root = path.join(global.__views_dir, '/images/bigcapital.png');
+    const root = path.join(global.__images_dirname, '/bigcapital.png');
     const baseURL = this.configService.get('baseURL');
 
     const mail = new Mail()