fix(dashboard): remove redundant settings shortcuts

[everpcpc]

Problem

The Dashboard showed a Settings gear on iPad and macOS even though both platforms already provide Settings through their navigation: the iPad tab/sidebar and the macOS Settings scene.

Fix

• Limit the Dashboard Settings shortcut to iPhone.
• Remove the unused macOS openSettings dependency.
• Update the platform toolbar conventions.

Validation

• make format completed successfully.
• make build passed for iOS, macOS, and tvOS.
• iPad Pro 13-inch simulator: the Dashboard shows Search without the Settings gear, and the Settings tab remains available.
• macOS manual check: the Dashboard toolbar shows the library scope and Search without the Settings gear.