BUG: Missing defer on temp file cleanup in attach handler

[andrinoff]

Describe the bug: Temp files created for attachments may not be cleaned up if errors occur after creation.

To reproduce:

1. Check attachment download code paths
2. If error occurs after temp file created but before cleanup
3. Temp files accumulate in system temp directory

Expected behavior: Use defer to ensure temp file cleanup even on error paths.

Additional context:

• Review view/html.go and attachment handling code
• Severity: Low-Medium - disk space leak
• Fix: Add defer os.Remove after temp file creation