Describe the bug

In tui/email_view.go:326-354, crypto status and shortcuts strings are built with +=:

cryptoStatus += lipgloss.NewStyle()...Render(" [PGP: 🔒 Encrypted]")
shortcuts += " • " + pk.Key + ": " + pk.Description
shortcuts += " • " + m.pluginStatus

To reproduce

Not a crash — code quality and minor performance issue.

Expected behavior

Use strings.Builder for building crypto status and shortcuts strings.