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

Sources/Secretive.xcodeproj/xcshareddata/xcschemes/SecretAgent.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1320"
+   LastUpgradeVersion = "2600"
    version = "1.7">
    <BuildAction
       parallelizeBuildables = "YES"

Sources/Secretive.xcodeproj/xcshareddata/xcschemes/Secretive.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1320"
+   LastUpgradeVersion = "2600"
    version = "1.7">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -89,7 +89,7 @@
       </BuildableProductRunnable>
    </LaunchAction>
    <ProfileAction
-      buildConfiguration = "Release"
+      buildConfiguration = "Debug"
       shouldUseLaunchSchemeArgsEnv = "YES"
       savedToolIdentifier = ""
       useCustomWorkingDirectory = "NO"