refactor: Updated Demo apps to both use Swift 6 and Strict Memory Safety

[hollyschilling-cio]

First, I'm not sure if calling this a refactor is appropriate or not. Code is only modified within the demo apps. If there is a better label for it, please let me know and I'll change it.

Both demo apps have been updated to use Strict Memory Safety with Swift 6. The SDK is completely unchanged and working in pre-concurrency mode with Swift 5.5

Please actually check out and build the demo apps while reviewing this PR. I'd like a bigger sample size than "it works on my machine."

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Note

Medium Risk
Medium risk because it upgrades build tooling (Xcode/Swift) and introduces concurrency annotations/locking that can affect runtime behavior and CI stability, though changes are largely confined to sample apps and test/util code.

Overview
Updates CI and release workflows to build sample apps with Xcode 26.2 / iOS 26, including updating the setup action reference, default Xcode version, and simplifying iOS platform download; Fastlane builds now force DWARF v4 debug info for bloaty compatibility.

Migrates both demo apps to Swift 6 + SWIFT_STRICT_MEMORY_SAFETY, adding @MainActor/nonisolated/@Sendable annotations, making the APN demo DI container (DIGraphShared) Sendable with lock-protected storage, and refactoring SwiftUI alert/push-permission flows (removing custom Binding helpers, using .alert(item:), async notification permission checks, and retroactive String: Identifiable).

Makes a few small SDK/internal cleanups to avoid unsafe optional mapping (mapNonNil -> compactMap, subview lookups via first(where:)) and updates unit tests to the Swift Testing framework.

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[github-actions]

Sample app builds 📱

Below you will find the list of the latest versions of the sample apps.
It's recommended to always download the latest builds to test this PR accurately.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.94%. Comparing base (7f81928) to head (333b575).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #983      +/-   ##
==========================================
+ Coverage   67.89%   67.94%   +0.05%     
==========================================
  Files         181      182       +1     
  Lines        9524     9506      -18     
==========================================
- Hits         6466     6459       -7     
+ Misses       3058     3047      -11     

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[mrehan27]

Tried running this locally and both apps compiled correctly for me. However, CI is failing and needs to be fixed before merging. Rest looks good.

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.