fix(ios): harden Apple discovery lifecycle

[dcavalcante]

Summary

• retain Apple discovery/pairing tasks atomically so parent teardown cannot leave orphan work
• retain data-path tasks atomically so an early terminal callback cannot race task ownership
• deduplicate publisher paired-device peers using Apple's stable WAPairedDevice.id
• log non-cancellation Apple discovery failures for physical-device diagnosis

Scope correction

I rechecked the current Apple Wi-Fi Aware guidance before implementation. The existing .finish(endpoint) subscriber flow matches Apple's WWDC sample, and the publisher NetworkListener belongs to the post-pairing connection flow, so this PR deliberately does not force Android discovery semantics onto those Apple APIs.

Validation

CI requested via this PR. Physical Apple-device validation remains pending by design.