feat(client): opt-in "Rumble on this phone" mirrors pad-0 rumble onto the device

iOS + Android: a new opt-in setting mirrors controller 1's rumble onto the
device's own actuator (Apple RumbleRenderer Actuator.device / CoreHaptics,
Android deviceBodyVibrator), so a motor-less clip-on pad still gives haptic
feedback through the phone/tablet it's clamped to. Default off; wired through
the gamepad settings on both platforms.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/Settings/SettingsView+Support.swift

@@ -88,6 +88,13 @@ extension SettingsView {
         + "controller (a DualSense keeps adaptive triggers, lightbar, touchpad and motion). "
         + "Applies from the next session."
 
+    #if os(iOS)
+    static let deviceRumbleFooter =
+        "Rumble on this iPhone plays player 1's rumble on the phone's own Taptic Engine as "
+        + "well — for clip-on controllers that have no rumble motors of their own. Applies "
+        + "from the next session."
+    #endif
+
     #if !os(tvOS)
     static let gamepadUIFooter =
         "When a controller connects, the host list and library switch to a controller-"