Swift 6 / Concurrency fixes (#578)

* Enable language mode

* WIP

* WIP

* Fix concurrency issues in SmartCardStore

* Switch to SMAppService

* Bump runners

* Base

* Finish Testing migration

* Tweak async for updater

* More

* Backport mutex

* Revert "Backport mutex"

This reverts commit 9b02afb20c.

* WIP

* Reenable

* Fix preview.

* Update package.

* Bump to latest public macOS and Xcode

* Bump back down to 6.1

* Update to Xcode 26.

* Fixed tests.

* More cleanup

* Env fixes

* var->let

* Cleanup

* Persist auth async

* Whitespace.

* Whitespace.

* Cleanup.

* Cleanup

* Redoing locks in actors bc of observable

* Actors.

* .

* Specify b5

* Update package to 6.2

* Fix disabled updater

* Remove preconcurrency warning

* Move updater init

.github/workflows/nightly.yml

@@ -20,7 +20,7 @@ jobs:
         APPLE_API_KEY_ID: ${{ secrets.APPLE_API_KEY_ID }}
       run: ./.github/scripts/signing.sh
     - name: Set Environment
-      run: sudo xcrun xcode-select -s /Applications/Xcode_16.4.app
+      run: sudo xcrun xcode-select -s /Applications/Xcode_26_beta_5.app
     - name: Update Build Number
       env:
         RUN_ID: ${{ github.run_id }}