feat(journal-inmemory): add :journal-inmemory module with InMemoryJournalStore

- Introduced a new `:journal-inmemory` module implementing `:journal-api` with an in-memory backend.
- Added `InMemoryJournalStore` for concurrent append, list, and clear operations using `Mutex` and `MutableList`.
- Use cases include tests, dev mode, embedded scenarios, and client-side in-process caching.
- Integrated the module into the project setup and documented usage in `:client/README.md`.
- Added comprehensive

settings.gradle.kts

@@ -90,6 +90,7 @@ include(":outbox-api")
 // KMP in-memory реализация MutableEventStore. ConcurrentLinkedDeque + TTL/size
 // eviction. Для тестов, dev-режима, embedded-сценариев (Android core).
 include(":outbox-inmemory")
+include(":journal-inmemory")
 //include(":event-store-in-memory")
 //include(":working-memory-api")
 include(":storage-inmemory")