fix(ios): prevent thread overload by reusing CHHapticEngine

[GorkaMinus]

Description

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:

• Reuse a single CHHapticEngine instance across multiple vibration calls
• Shut down the engine after duration + 5s of inactivity, so the idle countdown starts after the vibration finishes
• Handle engine lifecycle with resetHandler (restarts engine after server recovery) and stoppedHandler (clears the reference on external stops like audio interruptions or app suspension)

Change Type

• Fix

Rationale / Problems Fixed

Continuation of ionic-team/capacitor-plugins#2340, moved here per maintainer guidance since the haptics plugin now lives in its own repository.

Related: #7

Creating a new CHHapticEngine per vibrate() call spawns threads that accumulate faster than the system can reclaim them. Under rapid-fire usage (pickers, scroll-driven haptics), this leads to thread exhaustion, UI freezes, and eventual crashes.

Tests or Reproductions

• Rapidly call Haptics.vibrate() from a picker/scroll, confirm no freeze or crash
• Call vibrate(duration) with a long duration (e.g. 5s), confirm vibration completes fully before engine shuts down
• Trigger an audio session interruption (e.g. phone call) mid-session, confirm haptics recover on next use
• Verify fallback to AudioServicesPlayAlertSound on devices without haptic support

Platforms Affected

• iOS

Notes / Comments

This also addresses review feedback from the original PR (ionic-team/capacitor-plugins#2340):

• Removed redundant supportsHaptics check inside initializeEngine() since it's already guarded in the caller
• Idle timer now accounts for vibration duration (duration + 5s) instead of a flat 5s countdown
• Added resetHandler and stoppedHandler for proper engine lifecycle management following Apple's recommended patterns