fix(multi-account): preserve existing account when adding new one

- ensureCurrentAccountInStorage(): saves current account metadata to
  encrypted storage before switching to new account via AddAccountDialog
- AddAccountDialog calls ensureCurrentAccountInStorage() before each
  login method to prevent losing the previous account
- LoginScreen onLoginSuccess now calls refreshAccountList() so the
  switcher dropdown picks up the initial account immediately

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/Main.kt

@@ -708,6 +708,10 @@ fun App(
                             if (current?.signerType is com.vitorpamplona.amethyst.commons.model.account.SignerType.Remote) {
                                 accountManager.startHeartbeat(scope)
                             }
+                            // Refresh account list for switcher
+                            scope.launch(Dispatchers.IO) {
+                                accountManager.refreshAccountList()
+                            }
                         },
                     )
                 }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/account/AccountManager.kt

@@ -637,6 +637,17 @@ class AccountManager internal constructor(
         refreshAccountList()
     }
 
+    /**
+     * Ensures the currently logged-in account is persisted in multi-account storage.
+     * Call before switching to a new account to avoid losing the current one.
+     */
+    suspend fun ensureCurrentAccountInStorage() {
+        val current = currentAccount() ?: return
+        val info = AccountInfo(npub = current.npub, signerType = current.signerType)
+        accountStorage.saveAccount(info)
+        accountStorage.setCurrentAccount(current.npub)
+    }
+
     suspend fun removeAccountFromStorage(npub: String) {
         val current = currentAccount()
         accountStorage.deleteAccount(npub)

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/account/AddAccountDialog.kt

@@ -88,6 +88,12 @@ fun AddAccountDialog(
                 ) {
                     LoginCard(
                         onLogin = { keyInput ->
+                            // Save current account before switching
+                            scope.launch {
+                                withContext(Dispatchers.IO) {
+                                    accountManager.ensureCurrentAccountInStorage()
+                                }
+                            }
                             accountManager.loginWithKey(keyInput).map {
                                 scope.launch {
                                     withContext(Dispatchers.IO) { accountManager.saveCurrentAccount() }
@@ -96,18 +102,31 @@ fun AddAccountDialog(
                             }
                         },
                         onGenerateNew = {
-                            accountManager.generateNewAccount()
                             scope.launch {
+                                withContext(Dispatchers.IO) {
+                                    accountManager.ensureCurrentAccountInStorage()
+                                }
+                                accountManager.generateNewAccount()
                                 withContext(Dispatchers.IO) { accountManager.saveCurrentAccount() }
                                 onAccountAdded()
                             }
                         },
                         onLoginBunker = { bunkerUri ->
+                            scope.launch {
+                                withContext(Dispatchers.IO) {
+                                    accountManager.ensureCurrentAccountInStorage()
+                                }
+                            }
                             accountManager.loginWithBunker(bunkerUri).map {
                                 onAccountAdded()
                             }
                         },
                         onLoginNostrConnect = { onUriGenerated ->
+                            scope.launch {
+                                withContext(Dispatchers.IO) {
+                                    accountManager.ensureCurrentAccountInStorage()
+                                }
+                            }
                             accountManager.loginWithNostrConnect(onUriGenerated).map {
                                 onAccountAdded()
                             }