feat: auth screen with auto-redirect, sync favorites/history with backend

app/src/main/java/com/radiola/ui/auth/AuthViewModel.kt

@@ -0,0 +1,70 @@
+package com.radiola.ui.auth
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.radiola.domain.usecase.auth.RequestMagicLinkUseCase
+import com.radiola.domain.usecase.auth.VerifyMagicLinkUseCase
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+@HiltViewModel
+class AuthViewModel @Inject constructor(
+    private val requestMagicLinkUseCase: RequestMagicLinkUseCase,
+    private val verifyMagicLinkUseCase: VerifyMagicLinkUseCase
+) : ViewModel() {
+
+    sealed class AuthState {
+        data object Idle : AuthState()
+        data object Loading : AuthState()
+        data object CodeSent : AuthState()
+        data object Success : AuthState()
+        data class Error(val message: String) : AuthState()
+    }
+
+    private val _state = MutableStateFlow<AuthState>(AuthState.Idle)
+    val state: StateFlow<AuthState> = _state
+
+    private val _email = MutableStateFlow("")
+    val email: StateFlow<String> = _email
+
+    fun onEmailChange(value: String) {
+        _email.value = value
+    }
+
+    fun requestCode() {
+        val email = _email.value.trim()
+        if (email.isBlank() || !email.contains("@")) {
+            _state.value = AuthState.Error("Введите корректный email")
+            return
+        }
+        viewModelScope.launch {
+            _state.value = AuthState.Loading
+            requestMagicLinkUseCase(email)
+                .onSuccess { _state.value = AuthState.CodeSent }
+                .onFailure { _state.value = AuthState.Error(it.message ?: "Ошибка отправки") }
+        }
+    }
+
+    fun verifyCode(code: String) {
+        val email = _email.value.trim()
+        if (code.length != 6) {
+            _state.value = AuthState.Error("Код должен содержать 6 символов")
+            return
+        }
+        viewModelScope.launch {
+            _state.value = AuthState.Loading
+            verifyMagicLinkUseCase(email, code)
+                .onSuccess { _state.value = AuthState.Success }
+                .onFailure { _state.value = AuthState.Error(it.message ?: "Неверный код") }
+        }
+    }
+
+    fun dismissError() {
+        if (_state.value is AuthState.Error) {
+            _state.value = AuthState.Idle
+        }
+    }
+}