perf: optimize startup, database, and ui rendering (#405)

* perf: optimize startup, database, and ui rendering

* fix(#405): address code review feedback

* test: wait for async prefs initialization to prevent coroutine leaks

* test: stub mockViewModel.streamingState in ChatScreenTest to prevent ClassCastException on Android

app/src/androidTest/java/com/m57/hermescontrol/ui/chat/ChatScreenTest.kt

@@ -54,6 +54,7 @@ class ChatScreenTest {
             )
         val mockViewModel = mockk<ChatViewModel>(relaxed = true)
         every { mockViewModel.uiState } returns MutableStateFlow(uiState).asStateFlow()
+        every { mockViewModel.streamingState } returns MutableStateFlow(StreamingState()).asStateFlow()
 
         composeTestRule.setContent {
             ChatScreen(