Refactor: Extract boilerplate: safeLaunchLoad, clearToast, ToastEffect (CODE-21/22/23) (#312)

- Extracted `safeLaunchLoad` inline extension function to `ViewModelExt.kt` to encapsulate API call success/failure handling logic and replaced usages across 18 viewmodels.
- Extracted `ToastHost` interface to standardize `clearToast()` behavior across all ViewModels displaying toasts.
- Extracted `ToastEffect` composable to `SharedComponents.kt` and applied it to 16 screens, reducing repetitive side effect code blocks.

Fixes #286

app/src/main/java/com/m57/hermescontrol/ui/gateway/GatewayScreen.kt

@@ -1,6 +1,5 @@
 package com.m57.hermescontrol.ui.gateway
 
-import android.widget.Toast
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -31,7 +30,6 @@ import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
@@ -41,6 +39,7 @@ import com.m57.hermescontrol.R
 import com.m57.hermescontrol.ui.common.ErrorState
 import com.m57.hermescontrol.ui.common.HermesScaffold
 import com.m57.hermescontrol.ui.common.LoadingState
+import com.m57.hermescontrol.ui.common.ToastEffect
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -50,18 +49,12 @@ fun GatewayScreen(
     viewModel: GatewayViewModel = viewModel { GatewayViewModel() },
 ) {
     val state by viewModel.uiState.collectAsStateWithLifecycle()
-    val context = LocalContext.current
 
     LaunchedEffect(Unit) {
         viewModel.loadStatus()
     }
 
-    LaunchedEffect(state.toastMessage) {
-        state.toastMessage?.let { msg ->
-            Toast.makeText(context, msg, Toast.LENGTH_SHORT).show()
-            viewModel.clearToast()
-        }
-    }
+    ToastEffect(toastMessage = state.toastMessage, onClearToast = viewModel::clearToast)
 
     HermesScaffold(
         title = { Text(stringResource(R.string.screen_gateway)) },

app/src/main/java/com/m57/hermescontrol/ui/gateway/GatewayViewModel.kt

@@ -6,6 +6,8 @@ import com.m57.hermescontrol.data.model.StatusResponse
 import com.m57.hermescontrol.data.remote.ApiClient
 import com.m57.hermescontrol.data.remote.NetworkResult
 import com.m57.hermescontrol.data.remote.safeApiCall
+import com.m57.hermescontrol.ui.common.ToastHost
+import com.m57.hermescontrol.ui.common.safeLaunchLoad
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
@@ -22,32 +24,26 @@ data class GatewayUiState(
     val toastMessage: String? = null,
 )
 
-class GatewayViewModel : ViewModel() {
+class GatewayViewModel : ViewModel(), ToastHost {
     private val _uiState = MutableStateFlow(GatewayUiState())
     val uiState: StateFlow<GatewayUiState> = _uiState.asStateFlow()
 
     fun loadStatus() {
-        _uiState.update { it.copy(isLoading = true, errorMessage = null) }
-        viewModelScope.launch {
-            val result =
-                withContext(Dispatchers.IO) {
-                    safeApiCall { ApiClient.hermesApi.getStatus() }
+        safeLaunchLoad(
+            apiCall = { safeApiCall { ApiClient.hermesApi.getStatus() } },
+            onStart = { _uiState.update { it.copy(isLoading = true, errorMessage = null) } },
+            onSuccess = { data ->
+                _uiState.update { it.copy(isLoading = false, status = data) }
+            },
+            onError = { errorMsg ->
+                _uiState.update {
+                    it.copy(
+                        isLoading = false,
+                        errorMessage = "Failed to load status: $errorMsg",
+                    )
                 }
-            when (result) {
-                is NetworkResult.Success -> {
-                    _uiState.update { it.copy(isLoading = false, status = result.data) }
-                }
-
-                is NetworkResult.Failure -> {
-                    _uiState.update {
-                        it.copy(
-                            isLoading = false,
-                            errorMessage = "Failed to load status: ${result.error.message}",
-                        )
-                    }
-                }
-            }
-        }
+            },
+        )
     }
 
     fun startGateway() {
@@ -92,7 +88,7 @@ class GatewayViewModel : ViewModel() {
         }
     }
 
-    fun clearToast() {
+    override fun clearToast() {
         _uiState.update { it.copy(toastMessage = null) }
     }
 }