feat: Implement setup screen and login logic

- Add SetupScreen with UI for server URL, username, and password input.
- Make SetupScreen the initial screen in the navigation graph.
- Implement secure credential storage using EncryptedSharedPreferences.
- Create CredentialsRepository and AuthRepository to manage credentials and auth tokens.
- Add LoginUseCase to handle the business logic for logging in.
- Implement a temporary Retrofit client in ItemRepository to handle login against a user-provided URL.
- Integrate login logic into SetupViewModel.
- Update all relevant project documentation and DI modules.

domain/src/main/java/com/homebox/lens/domain/model/Credentials.kt

@@ -0,0 +1,18 @@
+// [PACKAGE] com.homebox.lens.domain.model
+// [FILE] Credentials.kt
+
+package com.homebox.lens.domain.model
+
+/**
+ * [CONTRACT]
+ * Data class to hold server credentials.
+ * @property serverUrl The URL of the Homebox server.
+ * @property username The username for authentication.
+ * @property password The password for authentication.
+ */
+data class Credentials(
+    val serverUrl: String,
+    val username: String,
+    val password: String
+)
+// [END_FILE_Credentials.kt]

domain/src/main/java/com/homebox/lens/domain/repository/AuthRepository.kt

@@ -0,0 +1,27 @@
+// [PACKAGE] com.homebox.lens.domain.repository
+// [FILE] AuthRepository.kt
+
+package com.homebox.lens.domain.repository
+
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * [CONTRACT]
+ * Repository for managing authentication tokens.
+ */
+interface AuthRepository {
+    /**
+     * [CONTRACT]
+     * Saves the authentication token.
+     * @param token The token to save.
+     */
+    suspend fun saveToken(token: String)
+
+    /**
+     * [CONTRACT]
+     * Retrieves the authentication token.
+     * @return A Flow emitting the token, or null if not found.
+     */
+    fun getToken(): Flow<String?>
+}
+// [END_FILE_AuthRepository.kt]

domain/src/main/java/com/homebox/lens/domain/repository/CredentialsRepository.kt

@@ -0,0 +1,28 @@
+// [PACKAGE] com.homebox.lens.domain.repository
+// [FILE] CredentialsRepository.kt
+
+package com.homebox.lens.domain.repository
+
+import com.homebox.lens.domain.model.Credentials
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * [CONTRACT]
+ * Repository for managing user credentials.
+ */
+interface CredentialsRepository {
+    /**
+     * [CONTRACT]
+     * Saves the user credentials securely.
+     * @param credentials The credentials to save.
+     */
+    suspend fun saveCredentials(credentials: Credentials)
+
+    /**
+     * [CONTRACT]
+     * Retrieves the saved user credentials.
+     * @return A Flow emitting the saved [Credentials], or null if none are saved.
+     */
+    fun getCredentials(): Flow<Credentials?>
+}
+// [END_FILE_CredentialsRepository.kt]

domain/src/main/java/com/homebox/lens/domain/repository/ItemRepository.kt

@@ -12,6 +12,7 @@ import com.homebox.lens.domain.model.*
  * Определяет контракт, которому должен следовать слой данных.
  */
 interface ItemRepository {
+    suspend fun login(credentials: Credentials): Result<Unit>
     suspend fun createItem(newItemData: ItemCreate): ItemSummary
     suspend fun getItemDetails(itemId: String): ItemOut
     suspend fun updateItem(itemId: String, item: ItemUpdate): ItemOut

domain/src/main/java/com/homebox/lens/domain/usecase/LoginUseCase.kt

@@ -0,0 +1,29 @@
+// [PACKAGE] com.homebox.lens.domain.usecase
+// [FILE] LoginUseCase.kt
+
+package com.homebox.lens.domain.usecase
+
+import com.homebox.lens.domain.model.Credentials
+import com.homebox.lens.domain.repository.ItemRepository
+import javax.inject.Inject
+import com.homebox.lens.domain.model.Result
+
+/**
+ * [CONTRACT]
+ * Use case for user login.
+ * @param itemRepository The repository to handle item and auth operations.
+ */
+class LoginUseCase @Inject constructor(
+    private val itemRepository: ItemRepository
+) {
+    /**
+     * [CONTRACT]
+     * Executes the login process.
+     * @param credentials The user's credentials.
+     * @return A [Result] object indicating success or failure.
+     */
+    suspend operator fun invoke(credentials: Credentials): Result<Unit> {
+        return itemRepository.login(credentials)
+    }
+}
+// [END_FILE_LoginUseCase.kt]