Fix: isolate auto-login errors from confirmation code errors

- confirmRegistration: wrap auto-login in separate try-catch so a failed
  login after confirmation never shows as 'wrong code' to the user.
  If auto-login fails, user is sent to LoginScreen to log in manually.
- SessionManager.login: always reconnect fresh (disconnect + enableReconnect
  + connect) instead of reusing the stale post-registration TCP connection.
  Fixes login failures caused by server closing the registration connection.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/src/main/java/com/kecalek/chat/core/SessionManager.kt

@@ -64,9 +64,9 @@ class SessionManager @Inject constructor(
         // Re-authenticate automatically whenever the connection is (re)established.
         // During the initial login() call, lastEmail is null (cleared before connect),
         // so this handler is a no-op for the first connection.
-        connection.onConnected = {
-            val email = lastEmail ?: return@onConnected
-            val key   = lastRsaPrivateKey ?: return@onConnected
+        connection.onConnected = reconnect@{
+            val email = lastEmail ?: return@reconnect
+            val key   = lastRsaPrivateKey ?: return@reconnect
             scope.launch {
                 try {
                     val session = performAuthHandshake(email, key, lastDeviceId, "Android")
@@ -100,9 +100,13 @@ class SessionManager @Inject constructor(
         lastRsaPrivateKey = null
 
         try {
-            if (connection.state.value != ConnectionManager.State.CONNECTED) {
-                connection.connect(host, port, useTls)
+            // Always start with a fresh connection.
+            // This handles stale post-registration connections and ensures reconnect is armed.
+            if (connection.state.value == ConnectionManager.State.CONNECTED) {
+                connection.disconnect()
             }
+            connection.enableReconnect()
+            connection.connect(host, port, useTls)
 
             val session = performAuthHandshake(email, rsaPrivateKey, deviceId, deviceName)
 

app/src/main/java/com/kecalek/chat/ui/auth/AuthViewModel.kt

@@ -211,32 +211,47 @@ class AuthViewModel @Inject constructor(
         viewModelScope.launch {
             _uiState.update { it.copy(isLoading = true, loadingMessage = "Potvrzuji kód…", error = null) }
             try {
+                // Step 1: Verify the email code — this is the only thing that should report
+                // "wrong code". Any error here is genuinely a bad/expired code.
                 sessionManager.confirmRegistration(email, code)
 
-                // Auto-login immediately after confirmation using the already-decrypted
-                // key material from register(). This avoids re-asking for the password.
+                // Step 2: Try auto-login using the key material saved during register().
+                // This is best-effort — failure here does NOT mean the code was wrong.
+                // On failure the user is sent back to LoginScreen to log in manually.
                 val auth = pendingAuth
+                var loggedIn = false
                 if (auth != null && auth.email == email) {
-                    _uiState.update { it.copy(loadingMessage = "Přihlašuji se…") }
-                    val state = _uiState.value
-                    sessionManager.login(
-                        email = email,
-                        rsaPrivateKey = auth.rsaPrivate,
-                        host = state.serverHost,
-                        port = state.serverPort,
-                        useTls = state.useTls,
-                    )
-                    // Init local DB encryption key (no password needed — bytes already decrypted)
-                    keyStorage.initLocalKey(auth.identityPrivateBytes)
-                    pendingAuth = null   // consumed — clear for security
+                    try {
+                        _uiState.update { it.copy(loadingMessage = "Přihlašuji se…") }
+                        val state = _uiState.value
+                        sessionManager.login(
+                            email = email,
+                            rsaPrivateKey = auth.rsaPrivate,
+                            host = state.serverHost,
+                            port = state.serverPort,
+                            useTls = state.useTls,
+                        )
+                        keyStorage.initLocalKey(auth.identityPrivateBytes)
+                        loggedIn = true
+                    } catch (loginEx: Exception) {
+                        // Auto-login failed (e.g. stale connection, transient server error).
+                        // Log it but don't surface to user as a "wrong code" error.
+                        android.util.Log.w(
+                            "AuthViewModel",
+                            "Auto-login after confirm failed, user must log in manually: ${loginEx.message}"
+                        )
+                    } finally {
+                        pendingAuth = null
+                    }
                 }
 
                 _uiState.update {
                     it.copy(
                         isLoading = false,
                         loadingMessage = null,
-                        isLoggedIn = true,
+                        isLoggedIn = loggedIn,
                         needsConfirmation = false,
+                        hasExistingAccount = true,
                     )
                 }
             } catch (e: AuthException) {