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/PersonalDictionaryCloudSync/PersonalDictionaryCloudSync.swift

@@ -80,7 +80,12 @@ public final class PersonalDictionaryCloudSync {
     /// Enable sync: merge local + remote, persist locally, then upload.
     public func enableSync() async throws {
         let store = makeStore()
-        store.setPersonalDictionaryICloudSyncEnabled(true)
+        ICloudSyncPreferences.pushDictionaryEnabled(true, kvs: kvs)
+        ICloudSyncPreferences.cacheToAppGroup(
+            settingsEnabled: store.settingsICloudSyncEnabled,
+            dictionaryEnabled: true,
+            store: store
+        )
 
         let local = store.personalDictionary
         let remote = loadRemote() ?? .empty
@@ -90,7 +95,9 @@ public final class PersonalDictionaryCloudSync {
     }
 
     public func disableSync() {
-        makeStore().setPersonalDictionaryICloudSyncEnabled(false)
+        let store = makeStore()
+        ICloudSyncPreferences.pushDictionaryEnabled(false, kvs: kvs)
+        store.setPersonalDictionaryICloudSyncEnabled(false)
     }
 
     // MARK: - Core operations