v2.3.6 — 10 Critical Bug Fixes

fix: v2.3.6 — 10 critical bug fixes across iOS and Android

iOS:
- ChainExecutor: withTimeout return value was discarded; chains always treated as succeeded
- ChainExecutor: CancellationException swallowed by catch(Exception); cancellation now propagates
- ChainExecutor: repeat() break was actually continue; replaced with for+break
- NativeTaskScheduler: enqueueChain hardcoded requiresNetworkConnectivity=true; now false
- IosFileStorage: close() did not await background scope cancellation; caused head_pointer.txt crashes on real devices
- IosEventStore: initial file creation silently ignored write errors (error=null)

Android:
- NativeTaskScheduler: exact trigger used epoch timestamp (~1.7T ms) as delay instead of delta
- NativeTaskScheduler: periodic work ignored flexMs; now uses two-param PeriodicWorkRequestBuilder
- NativeTaskScheduler: DEVICE_IDLE constraint detection was inverted (any{it!=} vs any{it==})
- NativeTaskScheduler: ContentUri buildWorkManagerConstraints overload missing systemConstraints

Also: iOS sample app fixed for iOS 13 deployment target (.banner requires iOS 14+)