Replaced static `Application` references with instance-based `App`
context across the codebase. Updated calls to `Application.RequestStop()`
and `Application.Screen` to use `App?.RequestStop()` and `App?.Screen`
for better encapsulation and flexibility.
Refactored test infrastructure to align with the new context, including
reintroducing `FakeApplicationFactory` and `FakeApplicationLifecycle`
for testing purposes. Improved logging, error handling, and test
clarity by adding `logWriter` support and simplifying test setup.
Removed redundant or obsolete code, such as `NetSequences` and the old
`FakeApplicationFactory` implementation. Updated documentation to
reflect the new `IApplication.RequestStop()` usage.
