feat: implement persistent device flow polling and manual status refresh

- Implement `SavedStateHandle` in `AuthenticationViewModel` to persist and restore device flow session state across process death.
- Add background polling for GitHub device tokens using a dedicated `pollingJob` with a 15-second interval.
- Update `AuthenticationRepository` to support single poll attempts with granular error handling for pending, expired, or denied authorizations.
- Enhance `AuthenticationRoot` UI with a "Check status" button to allow users to manually trigger a token poll.
- Add `OnResumed` lifecycle effect to automatically trigger a status check when the user returns to the app from the browser.
- Include new localized strings for polling status and manual refresh actions.
- Improve error categorization and logging for the authentication workflow.

Author: rainxchzed

core/presentation/src/commonMain/composeResources/values/strings.xml

@@ -444,6 +444,8 @@
     <string name="auth_hint_try_again">Please try signing in again to get a new code.</string>
     <string name="auth_hint_check_connection">Please check your internet connection and try again.</string>
     <string name="auth_hint_denied">You denied the authorization request. Try again if this was unintentional.</string>
+    <string name="auth_check_status">I already authorized</string>
+    <string name="auth_polling_status">Checking…</string>
 
     <!-- Read More / Show Less -->
     <string name="read_more">Read More</string>

feature/auth/data/src/commonMain/kotlin/zed/rainxch/auth/data/repository/AuthenticationRepositoryImpl.kt

@@ -223,6 +223,61 @@ class AuthenticationRepositoryImpl(
         }
     }
 
+    override suspend fun pollDeviceTokenOnce(deviceCode: String): Result<GithubDeviceTokenSuccess?> =
+        withContext(Dispatchers.IO) {
+            val clientId = BuildKonfig.GITHUB_CLIENT_ID
+            try {
+                val res = GitHubAuthApi.pollDeviceToken(clientId, deviceCode)
+                val success = res.getOrNull()?.toDomain()
+
+                if (success != null) {
+                    logger.debug("✅ Single poll: Token received! Saving...")
+                    saveTokenWithVerification(success)
+                    Result.success(success)
+                } else {
+                    val error = res.exceptionOrNull()
+                    val errorMsg = (error?.message ?: "").lowercase()
+
+                    when {
+                        "authorization_pending" in errorMsg || "slow_down" in errorMsg -> {
+                            Result.success(null)
+                        }
+
+                        "access_denied" in errorMsg -> {
+                            Result.failure(
+                                Exception("Authentication was denied. Please try again if this was a mistake."),
+                            )
+                        }
+
+                        "expired_token" in errorMsg ||
+                            "expired_device_code" in errorMsg ||
+                            "token_expired" in errorMsg -> {
+                            Result.failure(
+                                Exception("Authorization code expired. Please try again."),
+                            )
+                        }
+
+                        "bad_verification_code" in errorMsg ||
+                            "incorrect_device_code" in errorMsg -> {
+                            Result.failure(
+                                Exception("Invalid verification code. Please restart authentication."),
+                            )
+                        }
+
+                        else -> {
+                            logger.debug("⚠️ Single poll unknown error: $errorMsg")
+                            Result.success(null)
+                        }
+                    }
+                }
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                logger.debug("⚠️ Single poll network error: ${e.message}")
+                Result.success(null)
+            }
+        }
+
     private fun isNetworkError(errorMsg: String): Boolean =
         errorMsg.contains("unable to resolve") ||
             errorMsg.contains("no address") ||

feature/auth/domain/src/commonMain/kotlin/zed/rainxch/auth/domain/repository/AuthenticationRepository.kt

@@ -10,4 +10,12 @@ interface AuthenticationRepository {
     suspend fun startDeviceFlow(): GithubDeviceStart
 
     suspend fun awaitDeviceToken(start: GithubDeviceStart): GithubDeviceTokenSuccess
+
+    /**
+     * Single poll attempt. Returns:
+     * - [Result.success] with non-null [GithubDeviceTokenSuccess] if user authorized
+     * - [Result.success] with null if authorization is still pending (keep polling)
+     * - [Result.failure] on terminal errors (denied, expired, invalid code)
+     */
+    suspend fun pollDeviceTokenOnce(deviceCode: String): Result<GithubDeviceTokenSuccess?>
 }

feature/auth/presentation/src/commonMain/kotlin/zed/rainxch/auth/presentation/AuthenticationAction.kt

@@ -22,4 +22,8 @@ sealed interface AuthenticationAction {
     ) : AuthenticationAction
 
     data object SkipLogin : AuthenticationAction
+
+    data object PollNow : AuthenticationAction
+
+    data object OnResumed : AuthenticationAction
 }

feature/auth/presentation/src/commonMain/kotlin/zed/rainxch/auth/presentation/AuthenticationRoot.kt

@@ -16,13 +16,15 @@ import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.ContentCopy
 import androidx.compose.material.icons.filled.DoneAll
 import androidx.compose.material.icons.filled.OpenWith
+import androidx.compose.material.icons.filled.Refresh
 import androidx.compose.material3.Card
 import androidx.compose.material3.CircularWavyProgressIndicator
 import androidx.compose.material3.ExperimentalMaterial3ExpressiveApi
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.IconButtonDefaults
 import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
@@ -37,6 +39,8 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.compose.LifecycleEventEffect
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import org.jetbrains.compose.resources.painterResource
 import org.jetbrains.compose.resources.stringResource
@@ -48,8 +52,10 @@ import zed.rainxch.core.presentation.theme.GithubStoreTheme
 import zed.rainxch.core.presentation.utils.ObserveAsEvents
 import zed.rainxch.githubstore.core.presentation.res.Res
 import zed.rainxch.githubstore.core.presentation.res.app_icon
+import zed.rainxch.githubstore.core.presentation.res.auth_check_status
 import zed.rainxch.githubstore.core.presentation.res.auth_code_expires_in
 import zed.rainxch.githubstore.core.presentation.res.auth_error_with_message
+import zed.rainxch.githubstore.core.presentation.res.auth_polling_status
 import zed.rainxch.githubstore.core.presentation.res.continue_as_guest
 import zed.rainxch.githubstore.core.presentation.res.copy_code
 import zed.rainxch.githubstore.core.presentation.res.enter_code_on_github
@@ -71,6 +77,10 @@ fun AuthenticationRoot(
 ) {
     val state by viewModel.state.collectAsStateWithLifecycle()
 
+    LifecycleEventEffect(Lifecycle.Event.ON_RESUME) {
+        viewModel.onAction(AuthenticationAction.OnResumed)
+    }
+
     ObserveAsEvents(viewModel.events) { event ->
         when (event) {
             AuthenticationEvents.OnNavigateToMain -> {
@@ -306,6 +316,32 @@ fun StateDevicePrompt(
             },
         )
 
+        Spacer(Modifier.height(12.dp))
+
+        OutlinedButton(
+            onClick = { onAction(AuthenticationAction.PollNow) },
+            enabled = !state.isPolling,
+            shape = RoundedCornerShape(16.dp),
+        ) {
+            Icon(
+                imageVector = Icons.Default.Refresh,
+                contentDescription = null,
+                modifier = Modifier.size(18.dp),
+            )
+
+            Spacer(Modifier.size(8.dp))
+
+            Text(
+                text =
+                    if (state.isPolling) {
+                        stringResource(Res.string.auth_polling_status)
+                    } else {
+                        stringResource(Res.string.auth_check_status)
+                    },
+                style = MaterialTheme.typography.bodyMedium,
+            )
+        }
+
         Spacer(Modifier.weight(2f))
     }
 }

feature/auth/presentation/src/commonMain/kotlin/zed/rainxch/auth/presentation/AuthenticationState.kt

@@ -6,4 +6,5 @@ data class AuthenticationState(
     val loginState: AuthLoginState = AuthLoginState.LoggedOut,
     val copied: Boolean = false,
     val info: String? = null,
+    val isPolling: Boolean = false,
 )