BGTaskScheduler.register(using: nil) invokes the handler on a background
queue, but the closure captured @MainActor-isolated self. Swift 6 runtime
enforces this with dispatch_assert_queue which crashed on Thread 4.
Fix: pass DispatchQueue.main as the handler queue so the callback runs
on the main queue, satisfying @MainActor isolation. Also fix expiration
handlers to capture a local Logger copy instead of accessing self.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
f10bc4fe59