docs(bulk-upload): explain chunkSize=10 and 50-file cap constants

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

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

@@ -134,6 +134,7 @@ public class DocumentService {
     }
 
     public void validateBatch(int fileCount, DocumentBatchMetadataDTO metadata) {
+        // 50-file hard cap keeps FormData requests at a manageable size and protects against runaway bulk uploads.
         if (fileCount > 50) {
             throw DomainException.badRequest(ErrorCode.BATCH_TOO_LARGE, "Batch exceeds maximum of 50 files per request");
         }

frontend/src/lib/components/document/BulkDocumentEditLayout.svelte

@@ -110,6 +110,7 @@ async function save() {
 	if (saving) return;
 	saving = true;
 	const entries = Array.from(files.values());
+	// 10 files per request keeps multipart bodies well under typical reverse-proxy limits (e.g. nginx default 1 MB client_max_body_size per PDF).
 	const chunkSize = 10;
 	const chunks: FileEntry[][] = [];
 	for (let i = 0; i < entries.length; i += chunkSize) {