feat: iCloud settings sync and cold-start return redesign

- Add iCloud key-value settings sync (engine/language/polish/Flow prefs);
  API keys stay on-device. New "Sync settings via iCloud" toggle.
- Redesign cold-start handoff: bottom-bar left-to-right swipe guidance,
  auto-dismiss on app switch, tap-anywhere to close, retained return link.
- Harden keyboard->app handoff with host-disconnected hint.
- Include prior Unreleased ASR fixes (route-change crash, fallback warning,
  multi-utterance recognition, local ASR diagnostics).

Release 0.5.0 (build 18).

OSGKeyboardShared/Services/KeyboardState.swift

@@ -80,7 +80,8 @@ public final class KeyboardState: ObservableObject {
     @Published public var onDeviceSupported: Bool = false
     /// Seconds remaining in the current utterance (Flow tap-to-talk).
     @Published public var utteranceRemainingSeconds: Int = Int(FlowSessionKeys.maxUtteranceDuration)
-    /// Whether the host app's Flow voice session is currently valid.
+    /// Whether the host app's Flow voice session is live and reachable (fresh
+    /// heartbeat). Do not use the App Group session flag alone for UI gating.
     @Published public var flowSessionActive: Bool = false
     /// When true, the mic is intentionally disabled (e.g. cloud engine
     /// selected but the provider-specific API key is missing).