feat(desktop-onboarding): neue Onboarding-UI implementiert, Backup- und Rollenmanagement hinzugefügt

- Einbindung eines komplett überarbeiteten Onboarding-Screens mit validierten Eingaben für Gerätename, Sicherheitsschlüssel und Backup-Pfad.
- `SettingsManager` eingeführt zur Speicherung der Onboarding-Daten in `settings.json`.
- Navigation verbessert: Onboarding-Workflow startet, wenn Konfiguration fehlt; neues "Setup"-Icon in der Navigationsleiste hinzugefügt.
- Backend: Geräte-API und `DeviceSecurityFilter` für Authentifizierung per Sicherheitsschlüssel implementiert.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

backend/services/identity/identity-infrastructure/src/main/kotlin/at/mocode/identity/infrastructure/persistence/DeviceTable.kt

@@ -0,0 +1,22 @@
+package at.mocode.identity.infrastructure.persistence
+
+import at.mocode.identity.domain.model.DeviceRole
+import org.jetbrains.exposed.v1.core.Table
+import org.jetbrains.exposed.v1.core.java.javaUUID
+import org.jetbrains.exposed.v1.datetime.timestamp
+
+/**
+ * Exposed Table definition für registrierte Desktop-Geräte.
+ */
+object DeviceTable : Table("identity_devices") {
+  val id = javaUUID("id").autoGenerate()
+  override val primaryKey = PrimaryKey(id)
+
+  val name = varchar("name", 100).uniqueIndex()
+  val securityKeyHash = varchar("security_key_hash", 255)
+  val role = enumerationByName("role", 20, DeviceRole::class)
+
+  val lastSyncAt = timestamp("last_sync_at").nullable()
+  val createdAt = timestamp("created_at")
+  val updatedAt = timestamp("updated_at")
+}

backend/services/identity/identity-infrastructure/src/main/kotlin/at/mocode/identity/infrastructure/persistence/ExposedDeviceRepository.kt

@@ -0,0 +1,72 @@
+package at.mocode.identity.infrastructure.persistence
+
+import at.mocode.identity.domain.model.Device
+import at.mocode.identity.domain.repository.DeviceRepository
+import org.jetbrains.exposed.v1.core.ResultRow
+import org.jetbrains.exposed.v1.core.eq
+import org.jetbrains.exposed.v1.jdbc.insert
+import org.jetbrains.exposed.v1.jdbc.selectAll
+import org.jetbrains.exposed.v1.jdbc.transactions.transaction
+import org.jetbrains.exposed.v1.jdbc.update
+import java.util.*
+import kotlin.time.Clock
+import kotlin.time.Instant
+import kotlin.time.toJavaInstant
+
+class ExposedDeviceRepository : DeviceRepository {
+
+  override suspend fun findById(id: UUID): Device? = transaction {
+    DeviceTable.selectAll().where { DeviceTable.id eq id }
+      .map { rowToDevice(it) }
+      .singleOrNull()
+  }
+
+  override suspend fun findByName(name: String): Device? = transaction {
+    DeviceTable.selectAll().where { DeviceTable.name eq name }
+      .map { rowToDevice(it) }
+      .singleOrNull()
+  }
+
+  override suspend fun save(device: Device): Device = transaction {
+    val now = Clock.System.now()
+    val existing = DeviceTable.selectAll().where { DeviceTable.id eq device.id }.singleOrNull()
+
+    if (existing != null) {
+      DeviceTable.update({ DeviceTable.id eq device.id }) {
+        it[name] = device.name
+        it[securityKeyHash] = device.securityKeyHash
+        it[role] = device.role
+        it[lastSyncAt] = device.lastSyncAt?.toJavaInstant()
+        it[updatedAt] = now.toJavaInstant()
+      }
+    } else {
+      DeviceTable.insert {
+        it[id] = device.id
+        it[name] = device.name
+        it[securityKeyHash] = device.securityKeyHash
+        it[role] = device.role
+        it[lastSyncAt] = device.lastSyncAt?.toJavaInstant()
+        it[createdAt] = now.toJavaInstant()
+        it[updatedAt] = now.toJavaInstant()
+      }
+    }
+    device
+  }
+
+  override suspend fun updateLastSyncAt(id: UUID, at: Instant): Boolean = transaction {
+    val javaInstant = at.toJavaInstant()
+    DeviceTable.update({ DeviceTable.id eq id }) {
+      it[lastSyncAt] = javaInstant
+      it[updatedAt] = javaInstant
+    } > 0
+  }
+
+  private fun rowToDevice(row: ResultRow): Device = Device(
+    id = row[DeviceTable.id],
+    name = row[DeviceTable.name],
+    securityKeyHash = row[DeviceTable.securityKeyHash],
+    role = row[DeviceTable.role],
+    lastSyncAt = row[DeviceTable.lastSyncAt]?.let { Instant.fromEpochMilliseconds(it.toEpochMilli()) },
+    createdAt = Instant.fromEpochMilliseconds(row[DeviceTable.createdAt].toEpochMilli())
+  )
+}