feat(backend): implement step 9 — REST controllers, DTOs, EntityService, SecurityConfig (permit-all)

backend/src/main/kotlin/com/condado/newsletter/dto/VirtualEntityCreateDto.kt

@@ -0,0 +1,14 @@
+package com.condado.newsletter.dto
+
+import jakarta.validation.constraints.Email
+import jakarta.validation.constraints.NotBlank
+
+/** DTO for creating a new [com.condado.newsletter.model.VirtualEntity]. */
+data class VirtualEntityCreateDto(
+    @field:NotBlank val name: String,
+    @field:NotBlank @field:Email val email: String,
+    @field:NotBlank val jobTitle: String,
+    val personality: String? = null,
+    val scheduleCron: String? = null,
+    val contextWindowDays: Int = 3
+)