[BE-07] Set up Nodemailer email service with transactional email templates

[yusuftomilola]

Overview

nodemailer is installed but never configured. Email is required for: password reset links, 2FA backup codes, maintenance due alerts, warranty expiry notifications, and scheduled report delivery. This issue creates the shared mail infrastructure.

Context

• package.json has nodemailer@7.0.12
• backend/.env.example already defines MAIL_FROM, SMTP_HOST, SMTP_PORT, SMTP_SECURE, SMTP_USER, SMTP_PASS
• Email sending must be async (enqueued via BullMQ from BE-04) so it never blocks HTTP responses
• Templates must be clean and branded — include AssetsUp name, relevant details, and a clear call-to-action

Acceptance Criteria

• Create src/mail/mail.module.ts and src/mail/mail.service.ts using nodemailer.createTransport() with SMTP config from ConfigService
• Create src/mail/templates/ directory with HTML string templates for: welcome.ts, password-reset.ts, otp-code.ts, maintenance-alert.ts, warranty-alert.ts
• MailService.sendMail({ to, subject, html }) wraps the transporter and catches SMTP errors without crashing the app
• Create a BullMQ mail processor (src/mail/mail.processor.ts) that dequeues and sends email jobs from the MAIL_QUEUE
• Add MailModule to AppModule imports and export MailService for other modules to inject
• In NODE_ENV=development, log the email content to the console instead of sending (use Ethereal Mail or similar for local testing)

[aigbagbobila]

@aigbagbobila has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi Maintainer can I resolve this issue. Kindly assign

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[devcarole]

@devcarole has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

GM, I would like to work on this issue.

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[portableDD]

@portableDD has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

can i work on this?

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