feat: implement VirtualEntity and DispatchLog models with corresponding tests and configuration

backend/src/main/kotlin/com/condado/newsletter/model/VirtualEntity.kt

@@ -0,0 +1,49 @@
+package com.condado.newsletter.model
+
+import jakarta.persistence.Column
+import jakarta.persistence.Entity
+import jakarta.persistence.GeneratedValue
+import jakarta.persistence.GenerationType
+import jakarta.persistence.Id
+import jakarta.persistence.Table
+import org.hibernate.annotations.CreationTimestamp
+import java.time.LocalDateTime
+import java.util.UUID
+
+/**
+ * Represents a fictional employee of "Condado Abaixo da Média SA".
+ * Each entity has a scheduled time to send AI-generated emails, a personality description,
+ * and a context window for reading recent emails via IMAP.
+ */
+@Entity
+@Table(name = "virtual_entities")
+class VirtualEntity(
+    @Column(nullable = false)
+    val name: String,
+
+    @Column(unique = true, nullable = false)
+    val email: String,
+
+    @Column(name = "job_title", nullable = false)
+    val jobTitle: String,
+
+    @Column(columnDefinition = "TEXT")
+    val personality: String? = null,
+
+    @Column(name = "schedule_cron")
+    val scheduleCron: String? = null,
+
+    @Column(name = "context_window_days")
+    val contextWindowDays: Int = 3,
+
+    @Column(nullable = false)
+    val active: Boolean = true
+) {
+    @Id
+    @GeneratedValue(strategy = GenerationType.UUID)
+    var id: UUID? = null
+
+    @CreationTimestamp
+    @Column(name = "created_at", updatable = false)
+    var createdAt: LocalDateTime? = null
+}