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).

OSGKeyboardTests/FlowSessionBridgeTests.swift

@@ -23,6 +23,40 @@ final class FlowSessionBridgeTests: XCTestCase {
         defaults.set(staleHeartbeat, forKey: FlowSessionKeys.flowHeartbeat)
         XCTAssertTrue(FlowSessionBridge.isSessionActive(defaults: defaults))
         XCTAssertFalse(FlowSessionBridge.isHostReachable(defaults: defaults))
+        XCTAssertFalse(FlowSessionBridge.isHostStale(defaults: defaults))
+    }
+
+    func testHostStaleWhenHeartbeatVeryOld() {
+        let defaults = makeDefaults()
+        FlowSessionBridge.markSessionActive(duration: 3_600, defaults: defaults)
+        let zombieHeartbeat = Date().timeIntervalSince1970 - 120
+        defaults.set(zombieHeartbeat, forKey: FlowSessionKeys.flowHeartbeat)
+
+        XCTAssertTrue(FlowSessionBridge.isSessionActive(defaults: defaults))
+        XCTAssertFalse(FlowSessionBridge.isHostReachable(defaults: defaults))
+        XCTAssertTrue(FlowSessionBridge.isHostStale(defaults: defaults))
+    }
+
+    func testClearIfHostStaleRemovesZombieSession() {
+        let defaults = makeDefaults()
+        FlowSessionBridge.markSessionActive(duration: 3_600, defaults: defaults)
+        FlowSessionBridge.setRecordingState(.stopped, defaults: defaults)
+        let zombieHeartbeat = Date().timeIntervalSince1970 - 120
+        defaults.set(zombieHeartbeat, forKey: FlowSessionKeys.flowHeartbeat)
+
+        XCTAssertTrue(FlowSessionBridge.clearIfHostStale(defaults: defaults))
+        XCTAssertFalse(FlowSessionBridge.isSessionActive(defaults: defaults))
+        XCTAssertEqual(FlowSessionBridge.recordingState(defaults: defaults), .idle)
+    }
+
+    func testHostStaleWhenSessionActiveButNoHeartbeat() {
+        let defaults = makeDefaults()
+        defaults.set(true, forKey: FlowSessionKeys.flowSessionActive)
+        defaults.set(Date().timeIntervalSince1970 + 3_600, forKey: FlowSessionKeys.flowSessionExpires)
+
+        XCTAssertTrue(FlowSessionBridge.isHostStale(defaults: defaults))
+        XCTAssertTrue(FlowSessionBridge.clearIfHostStale(defaults: defaults))
+        XCTAssertFalse(FlowSessionBridge.isSessionActive(defaults: defaults))
     }
 
     func testSessionInactiveWhenExpired() {