feat(person): add findTopByDocumentCount endpoint for reader dashboard

PersonController GET /api/persons?sort=documentCount&size=N returns the top N
persons by combined sender+receiver document count for the reader dashboard.

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

backend/src/main/java/org/raddatz/familienarchiv/person/PersonController.java

@@ -35,7 +35,13 @@ public class PersonController {
 
     @GetMapping
     @RequirePermission(Permission.READ_ALL)
-    public ResponseEntity<List<PersonSummaryDTO>> getPersons(@RequestParam(required = false) String q) {
+    public ResponseEntity<List<PersonSummaryDTO>> getPersons(
+            @RequestParam(required = false) String q,
+            @RequestParam(required = false, defaultValue = "0") int size,
+            @RequestParam(required = false) String sort) {
+        if ("documentCount".equals(sort) && size > 0 && q == null) {
+            return ResponseEntity.ok(personService.findTopByDocumentCount(size));
+        }
         return ResponseEntity.ok(personService.findAll(q));
     }
 

backend/src/main/java/org/raddatz/familienarchiv/person/PersonRepository.java

@@ -69,6 +69,20 @@ public interface PersonRepository extends JpaRepository<Person, UUID> {
             nativeQuery = true)
     List<PersonSummaryDTO> searchWithDocumentCount(@Param("query") String query);
 
+    @Query(value = """
+            SELECT p.id, p.title, p.first_name AS firstName, p.last_name AS lastName,
+                   p.person_type AS personType,
+                   p.alias, p.birth_year AS birthYear, p.death_year AS deathYear, p.notes,
+                   p.family_member AS familyMember,
+                   (SELECT COUNT(*) FROM documents d WHERE d.sender_id = p.id)
+                   + (SELECT COUNT(*) FROM document_receivers dr WHERE dr.person_id = p.id) AS documentCount
+            FROM persons p
+            ORDER BY documentCount DESC
+            LIMIT :limit
+            """,
+            nativeQuery = true)
+    List<PersonSummaryDTO> findTopByDocumentCount(@Param("limit") int limit);
+
     // --- Correspondent queries ---
 
     @Query(value = """

backend/src/main/java/org/raddatz/familienarchiv/person/PersonService.java

@@ -41,6 +41,10 @@ public class PersonService {
         return personRepository.searchWithDocumentCount(q.trim());
     }
 
+    public List<PersonSummaryDTO> findTopByDocumentCount(int limit) {
+        return personRepository.findTopByDocumentCount(limit);
+    }
+
     public Person getById(UUID id) {
         return personRepository.findById(id)
                 .orElseThrow(() -> DomainException.notFound(ErrorCode.PERSON_NOT_FOUND, "Person not found: " + id));