feat(#369): rewrite channels tab with full backend integration (#417)

* feat(#369): rewrite channels tab with full backend integration

- Add state, error, gateway_running, description to model
- Add test endpoint to API service
- Rewrite ViewModel with toggle, restart, test actions
- Rewrite screen with state badges, restart banner, test button
- Fix string resources and E2E test

* fix(#417): add missing import and fix ButtonSize API

- Add MessagingPlatformTestResult import to HermesApiService.kt
- Replace ButtonDefaults.ButtonSize.SMALL with ButtonDefaults.SmallButtonSize (correct M3 API)

* fix(#417): mark platformStateStyle as @Composable, remove Button size param
- @Composable annotation needed for MaterialTheme.colorScheme access
- Button/OutlinedButton size parameter not available in project's M3 version
- ktlint removed unused ButtonDefaults import

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

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

@@ -5,8 +5,14 @@ import com.google.gson.annotations.SerializedName
 data class MessagingPlatform(
     val id: String,
     val name: String,
+    val description: String? = null,
+    @SerializedName("docs_url") val docsUrl: String? = null,
     val enabled: Boolean,
     val configured: Boolean,
+    @SerializedName("gateway_running") val gatewayRunning: Boolean = false,
+    val state: String = "disabled",
+    @SerializedName("error_code") val errorCode: String? = null,
+    @SerializedName("error_message") val errorMessage: String? = null,
     @SerializedName("env_vars") val envVars: List<EnvVarField>? = null,
 )
 
@@ -14,9 +20,19 @@ data class EnvVarField(
     val key: String,
     val required: Boolean,
     @SerializedName("is_set") val isSet: Boolean,
-    val description: String?,
-    val prompt: String?,
+    @SerializedName("redacted_value") val redactedValue: String? = null,
+    val description: String? = null,
+    val prompt: String? = null,
+    val help: String? = null,
     @SerializedName("is_password") val isPassword: Boolean,
+    val advanced: Boolean = false,
+    val url: String? = null,
+)
+
+data class MessagingPlatformResponse(
+    @SerializedName("env_path") val envPath: String,
+    @SerializedName("gateway_start_command") val gatewayStartCommand: String,
+    val platforms: List<MessagingPlatform>,
 )
 
 data class MessagingPlatformUpdate(
@@ -25,3 +41,9 @@ data class MessagingPlatformUpdate(
     @SerializedName("clear_env") val clearEnv: List<String> = emptyList(),
     val profile: String? = null,
 )
+
+data class MessagingPlatformTestResult(
+    val ok: Boolean,
+    val state: String,
+    val message: String,
+)

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

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