What changed?

Added validation in DiscoveryScanView that checks whether the connected node's primary channel uses the default PSK (0x01). When it doesn't:

• An inline orange warning label is shown in the idle state
• The "Start Scan" button is disabled
• An alert is presented on view appear explaining the requirement

private var primaryChannelUsesDefaultKey: Bool {
    guard let channels = connectedNode?.myInfo?.channels else { return true }
    guard let primaryChannel = channels.first(where: { $0.role == 1 }) else { return true }
    let defaultKey = Data([0x01])
    return primaryChannel.psk == nil || primaryChannel.psk == defaultKey || primaryChannel.psk?.isEmpty == true
}

Why did it change?

Discovery scanning requires the default key on the primary channel to function correctly. Without this guard, users could initiate scans that would fail silently or produce incorrect results.

How is this tested?

Manual verification with nodes configured with both default and non-default primary channel keys. Confirmed the button disables, warning displays, and alert presents only when PSK ≠ default.

Screenshots/Videos (when applicable)

Checklist

• My code adheres to the project's coding and style guidelines.
• I have conducted a self-review of my code.
• I have commented my code, particularly in complex areas.
• I have verified whether these changes require an update to existing documentation or if new documentation is needed, and created an issue in the docs repo if applicable.
• I have tested the change to ensure that it works as intended.