Fix file retention after updates on macOS #417

This fixes issue #417 where autoupdate installer files were not deleted
on macOS, leading to accumulation of old installers.

Key changes:

- Store update files in application-specific directory
- Clear update files directory on every app launch

Other supporting changes:

- Refactor file system operations to be more testable and reusable
- Improve separation of concerns in directory management
- Enhance dependency injection for auto-update logic
- Fix async completion to support `await` operations
- Add additional logging and revise some log messages during updates

tests/unit/shared/Stubs/ReadbackFileWriterStub.ts

@@ -1,4 +1,4 @@
-import type { FileWriteErrorType, FileWriteOutcome, ReadbackFileWriter } from '@/infrastructure/ReadbackFileWriter/ReadbackFileWriter';
+import type { FileWriteErrorType, FileWriteOutcome, ReadbackFileWriter } from '@/infrastructure/FileSystem/ReadbackFileWriter/ReadbackFileWriter';
 import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
 
 export class ReadbackFileWriterStub