feat: Integrate AccountManager to retrieve last logged account in AuthFlow and update MainActivity

app/src/main/java/com/rosetta/messenger/ui/auth/AuthFlow.kt

@@ -5,6 +5,7 @@ import androidx.compose.animation.*
 import androidx.compose.animation.core.tween
 import androidx.compose.runtime.*
 import com.rosetta.messenger.data.DecryptedAccount
+import com.rosetta.messenger.data.AccountManager
 
 enum class AuthScreen {
     SELECT_ACCOUNT,
@@ -21,6 +22,7 @@ fun AuthFlow(
     isDarkTheme: Boolean,
     hasExistingAccount: Boolean,
     accounts: List<AccountInfo> = emptyList(),
+    accountManager: AccountManager,
     onAuthComplete: (DecryptedAccount?) -> Unit,
     onLogout: () -> Unit = {}
 ) {
@@ -33,7 +35,12 @@ fun AuthFlow(
         ) 
     }
     var seedPhrase by remember { mutableStateOf<List<String>>(emptyList()) }
-    var selectedAccountId by remember { mutableStateOf<String?>(accounts.firstOrNull()?.id) }
+    // Use last logged account or fallback to first account
+    var selectedAccountId by remember { 
+        mutableStateOf<String?>(
+            accountManager.getLastLoggedPublicKey() ?: accounts.firstOrNull()?.id
+        ) 
+    }
     var showCreateModal by remember { mutableStateOf(false) }
     
     // Handle system back button