feat(model): add title, personType, displayName to Person entity

- Add title (nullable VARCHAR) and personType (enum, default PERSON)
- Make firstName nullable for non-person entities
- Add @Transient getDisplayName() as single source of truth for
  name display, exposed via @Schema(READ_ONLY, REQUIRED)

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

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

@@ -21,14 +21,22 @@ public class Person {
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
     private UUID id;
 
-    @Column(nullable = false)
+    @Column(name = "title")
-    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private String title;
+
+    @Column(nullable = true)
     private String firstName;
 
     @Column(nullable = false)
     @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
     private String lastName;
 
+    @Enumerated(EnumType.STRING)
+    @Column(name = "person_type", nullable = false)
+    @Builder.Default
+    @Schema(requiredMode = Schema.RequiredMode.REQUIRED)
+    private PersonType personType = PersonType.PERSON;
+
     // Optional: Aliasse für die Suche (z.B. "Opa Hans")
     private String alias;
 
@@ -46,4 +54,14 @@ public class Person {
     @JsonIgnore
     @Builder.Default
     private List<PersonNameAlias> nameAliases = new ArrayList<>();
+
+    @Transient
+    @Schema(accessMode = Schema.AccessMode.READ_ONLY, requiredMode = Schema.RequiredMode.REQUIRED)
+    public String getDisplayName() {
+        StringBuilder sb = new StringBuilder();
+        if (title != null) sb.append(title).append(" ");
+        if (firstName != null) sb.append(firstName).append(" ");
+        sb.append(lastName);
+        return sb.toString().trim();
+    }
 }

backend/src/test/java/org/raddatz/familienarchiv/model/PersonTest.java

@@ -0,0 +1,53 @@
+package org.raddatz.familienarchiv.model;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class PersonTest {
+
+    @Test
+    void getDisplayName_withAllFields() {
+        Person person = Person.builder()
+                .title("Dr.")
+                .firstName("Walter")
+                .lastName("de Gruyter")
+                .build();
+        assertThat(person.getDisplayName()).isEqualTo("Dr. Walter de Gruyter");
+    }
+
+    @Test
+    void getDisplayName_withoutTitle() {
+        Person person = Person.builder()
+                .firstName("Clara")
+                .lastName("Cram")
+                .build();
+        assertThat(person.getDisplayName()).isEqualTo("Clara Cram");
+    }
+
+    @Test
+    void getDisplayName_withNullFirstName() {
+        Person person = Person.builder()
+                .lastName("Gesellschafter des Verlages")
+                .build();
+        assertThat(person.getDisplayName()).isEqualTo("Gesellschafter des Verlages");
+    }
+
+    @Test
+    void getDisplayName_withTitleAndNullFirstName() {
+        Person person = Person.builder()
+                .title("Tante")
+                .lastName("Molly")
+                .build();
+        assertThat(person.getDisplayName()).isEqualTo("Tante Molly");
+    }
+
+    @Test
+    void personType_defaultsToPerson() {
+        Person person = Person.builder()
+                .firstName("Clara")
+                .lastName("Cram")
+                .build();
+        assertThat(person.getPersonType()).isEqualTo(PersonType.PERSON);
+    }
+}