fix(metadata): preserve ISBN fields across metadata workflows

Carry ISBN-10 and ISBN-13 independently from accepted providers through
Auto-fill previews, saves and background refreshes. Preserve existing
identifiers and field locks, validate provider checksums and avoid
combining different editions.

Classify embedded ISBNs correctly and support ISBN-10 fallback in
search, Book Dock confidence and file naming.

packages/types/src/book.ts

@@ -349,6 +349,8 @@ export type BookMetadataSaveResult = {
 };
 
 export type BookMetadataRefreshPreviewFields = {
+  isbn10?: string | null;
+  isbn13?: string | null;
   title?: string | null;
   subtitle?: string | null;
   description?: string | null;

packages/types/src/metadata-preferences.ts

@@ -8,6 +8,7 @@ export type MetadataField =
   | "audioCover"
   | "authors"
   | "publisher"
+  | "isbn"
   | "publishedYear"
   | "language"
   | "pageCount"
@@ -27,6 +28,7 @@ export const ALL_METADATA_FIELDS: MetadataField[] = [
   "audioCover",
   "authors",
   "publisher",
+  "isbn",
   "publishedYear",
   "language",
   "pageCount",