fix backend startup imports

[Tomeshwari-02]

Summary

• add the missing backend logger utility imported by app startup code
• avoid constructing the Resend client until an email is actually sent
• remove duplicate/invalid Helmet options that prevented app construction

Why

The backend could not be imported from a fresh install because startup hit missing modules and module-load side effects before the Express app was created.

Fixes #1032

Validation

• node -e "import('./src/app.js').then(()=>console.log('ok')).catch(e=>{console.error(e.stack); process.exit(1)})" from backend

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