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

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

app/src/test/java/com/m57/hermescontrol/E2eIntegrationTest.kt

@@ -904,12 +904,19 @@ class E2eIntegrationTest {
     @Test
     fun testChannelsConfiguration_success() =
         runTest {
-            val platform = MessagingPlatform("telegram", "Telegram", false, false, emptyList())
+            val platform =
+                MessagingPlatform(
+                    id = "telegram",
+                    name = "Telegram",
+                    enabled = false,
+                    configured = false,
+                    envVars = emptyList(),
+                )
             coEvery { mockApiService.getMessagingPlatforms() } returns
                 Response.success(
                     MessagingPlatformResponse(
-                        env_path = "/tmp/.env",
-                        gateway_start_command = "hermes gateway start",
+                        envPath = "/tmp/.env",
+                        gatewayStartCommand = "hermes gateway start",
                         platforms = listOf(platform),
                     ),
                 )