fix(@capacitor/haptics): prevent thread overload by reusing CHHapticEngine

[GorkaMinus]

Fix: Prevent iOS app freeze by reusing CHHapticEngine instance

This PR addresses an issue where calling Haptics.vibrate() rapidly (e.g., from a fast-scrolling picker in my case) causes the app to hang or crash on iOS. The problem stems from creating a new CHHapticEngine instance on each call, which leads to excessive thread creation and eventual system overload.

Solution

• Reuses a single CHHapticEngine instance across multiple vibration calls.
• Ensures the engine is only created and started when necessary.
• Handles engine lifecycle and failure states gracefully.

This fix improves performance and stability, especially in high-frequency vibration scenarios.

Related Issue #1960