feat: parse and display all available EPUB metadata fields

Add parsing for dc:publisher, dc:date, dc:subject, dc:rights,
dc:contributor, dc:identifier (prefers ISBN scheme), and
calibre:rating. All new fields serialized in BookMetadataCache
(version bumped to 7) and displayed in BookInfoActivity with
rating shown as N/5 scale.

Made-with: Cursor

lib/I18n/I18nKeys.h

@@ -452,6 +452,13 @@ enum class StrId : uint16_t {
   STR_SERIES,
   STR_FILE_SIZE,
   STR_DESCRIPTION,
+  STR_PUBLISHER,
+  STR_DATE,
+  STR_SUBJECTS,
+  STR_RATING,
+  STR_ISBN,
+  STR_RIGHTS,
+  STR_CONTRIBUTOR,
   STR_MANAGE,
   STR_INFO,
   STR_ARCHIVE_BOOK,

lib/I18n/translations/english.yaml

@@ -399,6 +399,13 @@ STR_AUTHOR: "Author"
 STR_SERIES: "Series"
 STR_FILE_SIZE: "File Size"
 STR_DESCRIPTION: "Description"
+STR_PUBLISHER: "Publisher"
+STR_DATE: "Date"
+STR_SUBJECTS: "Subjects"
+STR_RATING: "Rating"
+STR_ISBN: "ISBN"
+STR_RIGHTS: "Rights"
+STR_CONTRIBUTOR: "Contributor"
 STR_MANAGE: "Manage"
 STR_INFO: "Info"
 STR_ARCHIVE_BOOK: "Archive Book"