feat(model): add PersonNameAlias entity, type enum, repository, DTO

Introduces the alias domain model: entity with @ManyToOne to Person,
@OneToMany on Person for JPA graph navigation, repository with
sort_order queries, input DTO, and ALIAS_NOT_FOUND error code.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/dto/PersonNameAliasDTO.java

@@ -0,0 +1,9 @@
+package org.raddatz.familienarchiv.dto;
+
+import org.raddatz.familienarchiv.model.PersonNameAliasType;
+
+public record PersonNameAliasDTO(
+        String lastName,
+        String firstName,
+        PersonNameAliasType type
+) {}

backend/src/main/java/org/raddatz/familienarchiv/exception/ErrorCode.java

@@ -11,6 +11,8 @@ public enum ErrorCode {
     // --- Persons ---
     /** A person with the given ID does not exist. 404 */
     PERSON_NOT_FOUND,
+    /** A person name alias with the given ID does not exist. 404 */
+    ALIAS_NOT_FOUND,
 
     // --- Documents ---
     /** A document with the given ID does not exist. 404 */

backend/src/main/java/org/raddatz/familienarchiv/model/Person.java

@@ -1,9 +1,12 @@
 package org.raddatz.familienarchiv.model;
 
+import com.fasterxml.jackson.annotation.JsonIgnore;
 import io.swagger.v3.oas.annotations.media.Schema;
 import jakarta.persistence.*;
 import lombok.*;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.UUID;
 @Entity
 @Table(name = "persons")
@@ -35,4 +38,12 @@ public class Person {
 
     private Integer birthYear;
     private Integer deathYear;
+
+    // Entity-graph navigation for JPA JOIN queries (e.g. DocumentSpecifications.hasText).
+    // Uses entity relationship rather than cross-domain repository access, avoiding a
+    // separate DB roundtrip while respecting domain boundaries.
+    @OneToMany(mappedBy = "person", cascade = CascadeType.ALL, orphanRemoval = true)
+    @JsonIgnore
+    @Builder.Default
+    private List<PersonNameAlias> nameAliases = new ArrayList<>();
 }

backend/src/main/java/org/raddatz/familienarchiv/model/PersonNameAlias.java

@@ -0,0 +1,48 @@
+package org.raddatz.familienarchiv.model;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.persistence.*;
+import lombok.*;
+import org.hibernate.annotations.CreationTimestamp;
+
+import java.time.Instant;
+import java.util.UUID;
+
+@Entity
+@Table(name = "person_name_aliases")
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@Builder
+public class PersonNameAlias {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.UUID)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private UUID id;
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "person_id", nullable = false)
+    private Person person;
+
+    @Column(name = "last_name", nullable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String lastName;
+
+    @Column(name = "first_name")
+    private String firstName;
+
+    @Enumerated(EnumType.STRING)
+    @Column(nullable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private PersonNameAliasType type;
+
+    @Column(name = "sort_order", nullable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private Integer sortOrder;
+
+    @CreationTimestamp
+    @Column(name = "created_at", updatable = false)
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private Instant createdAt;
+}

backend/src/main/java/org/raddatz/familienarchiv/model/PersonNameAliasType.java

@@ -0,0 +1,8 @@
+package org.raddatz.familienarchiv.model;
+
+public enum PersonNameAliasType {
+    BIRTH,
+    WIDOWED,
+    DIVORCED,
+    OTHER
+}

backend/src/main/java/org/raddatz/familienarchiv/repository/PersonNameAliasRepository.java

@@ -0,0 +1,16 @@
+package org.raddatz.familienarchiv.repository;
+
+import org.raddatz.familienarchiv.model.PersonNameAlias;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+
+import java.util.List;
+import java.util.UUID;
+
+public interface PersonNameAliasRepository extends JpaRepository<PersonNameAlias, UUID> {
+
+    List<PersonNameAlias> findByPersonIdOrderBySortOrderAscCreatedAtAsc(UUID personId);
+
+    @Query("SELECT COALESCE(MAX(a.sortOrder), -1) FROM PersonNameAlias a WHERE a.person.id = :personId")
+    int findMaxSortOrder(UUID personId);
+}