fix(#248): add @Schema(REQUIRED) to TagTreeNodeDTO, improve mergeTags log, add comments

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

backend/src/main/java/org/raddatz/familienarchiv/controller/DocumentController.java

@@ -210,6 +210,8 @@ public class DocumentController {
         if (!"ASC".equalsIgnoreCase(dir) && !"DESC".equalsIgnoreCase(dir)) {
             throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "dir must be ASC or DESC");
         }
+        // tagOp is a raw String at the HTTP boundary; any value other than "OR" (case-insensitive)
+        // defaults to AND, which matches the frontend default and keeps old clients working.
         TagOperator operator = "OR".equalsIgnoreCase(tagOp) ? TagOperator.OR : TagOperator.AND;
         return ResponseEntity.ok(documentService.searchDocuments(q, from, to, senderId, receiverId, tags, tagQ, status, sort, dir, operator));
     }

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

@@ -6,9 +6,9 @@ import java.util.UUID;
 import io.swagger.v3.oas.annotations.media.Schema;
 
 public record TagTreeNodeDTO(
-        UUID id,
-        String name,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) UUID id,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String name,
         String color,
-        int documentCount,
+        @Schema(requiredMode = Schema.RequiredMode.REQUIRED) int documentCount,
         List<TagTreeNodeDTO> children,
         @Schema(description = "Parent tag ID, null for root tags") UUID parentId) {}

backend/src/main/java/org/raddatz/familienarchiv/service/TagService.java

@@ -79,10 +79,10 @@ public class TagService {
 
     @Transactional
     public Tag mergeTags(UUID sourceId, UUID targetId) {
-        log.info("Merging tag {} into {}", sourceId, targetId);
         validateNotSelf(sourceId, targetId);
-        getById(sourceId);
+        Tag source = getById(sourceId);
         Tag target = getById(targetId);
+        log.info("Merging tag '{}' ({}) into '{}' ({})", source.getName(), sourceId, target.getName(), targetId);
         validateNotDescendant(sourceId, targetId);
         transferDocuments(sourceId, targetId);
         tagRepository.reparentChildren(sourceId, targetId);
@@ -145,6 +145,8 @@ public class TagService {
     /**
      * Returns all tags assembled into a tree with document counts per node.
      * Uses a single aggregate query to avoid N+1 behaviour.
+     * NOTE: document counts are global per tag, not scoped to any search filter.
+     * The tree endpoint is only used for the admin sidebar, so this is intentional.
      */
     public List<TagTreeNodeDTO> getTagTree() {
         List<Tag> all = tagRepository.findAll();