fix: 401 logout loop — sync state update, prevent re-navigation

Root cause: LoginViewModel.logout() was async (viewModelScope.launch),
so _uiState.isConnected remained true after navigating to login.
LoginScreen's LaunchedEffect immediately navigated back to dashboard,
where APIs failed with 401 again → infinite loop.

Fixes:
- SessionManager: add _invalidating flag to prevent concurrent 401 handling
- AuthInterceptor: check isSessionValid before invalidating
- LoginViewModel: update _uiState synchronously in logout(), clear token
  before launching coroutine for prefs.clear()
- LoginViewModel: call SessionManager.restoreSession() after successful login
- MainActivity: remove restoreSession() from logout handler (was incorrectly
  re-validating session right after invalidation)

Bump to v1.7.1 (versionCode 10)

android/app/build.gradle.kts

@@ -12,8 +12,8 @@ android {
         applicationId = "com.devlab.app"
         minSdk = 26
         targetSdk = 37
-        versionCode = 9
-        versionName = "1.7.0"
+        versionCode = 10
+        versionName = "1.7.1"
     }
 
     buildTypes {