fix(#201): fix platforms endpoint response shape mismatch

GET /api/messaging/platforms returns a JSON object with a platforms
array inside, but the app expected a bare array. Wraps the response
in a new MessagingPlatformResponse model.

- Adds MessagingPlatformResponse.kt wrapper model
- Updates HermesApiService.kt return type + adds profile query param
- Updates ChannelsViewModel.kt to unwrap .platforms
- Updates E2eIntegrationTest.kt mock to match new response shape

app/src/main/java/com/m57/hermescontrol/data/model/MessagingPlatformResponse.kt

@@ -0,0 +1,7 @@
+package com.m57.hermescontrol.data.model
+
+data class MessagingPlatformResponse(
+    val env_path: String,
+    val gateway_start_command: String,
+    val platforms: List<MessagingPlatform>,
+)

app/src/main/java/com/m57/hermescontrol/data/remote/HermesApiService.kt

@@ -16,7 +16,7 @@ import com.m57.hermescontrol.data.model.KanbanTask
 import com.m57.hermescontrol.data.model.LogResponse
 import com.m57.hermescontrol.data.model.McpServerToggleRequest
 import com.m57.hermescontrol.data.model.McpServersResponse
-import com.m57.hermescontrol.data.model.MessagingPlatform
+import com.m57.hermescontrol.data.model.MessagingPlatformResponse
 import com.m57.hermescontrol.data.model.MessagingPlatformUpdate
 import com.m57.hermescontrol.data.model.ModelOptionsResponse
 import com.m57.hermescontrol.data.model.PairingApproveRequest
@@ -253,7 +253,7 @@ interface HermesApiService {
     ): Response<Unit>
 
     @GET("api/messaging/platforms")
-    suspend fun getMessagingPlatforms(): Response<List<MessagingPlatform>>
+    suspend fun getMessagingPlatforms(@Query("profile") profile: String? = null): Response<MessagingPlatformResponse>
 
     @PUT("api/messaging/platforms/{platform_id}")
     suspend fun configurePlatform(

app/src/main/java/com/m57/hermescontrol/ui/channels/ChannelsViewModel.kt

@@ -35,7 +35,7 @@ class ChannelsViewModel : ViewModel() {
                 }
             when (result) {
                 is NetworkResult.Success -> {
-                    _uiState.update { it.copy(isLoading = false, platforms = result.data.orEmpty()) }
+                    _uiState.update { it.copy(isLoading = false, platforms = result.data?.platforms.orEmpty()) }
                 }
 
                 is NetworkResult.Failure -> {