feat(library): add "Progress Read" sort option (#4427) (#4893)

Sort the library by reading progress (current/total pages). Books that
have never been opened read 0% and sort to the unread end; groups sort
by their most-progressed book. Direction reuses the existing
ascending/descending toggle, so "most read first" is Descending.

Adds the "Progress Read" entry to the Sort by menu and translates it
across all locales.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/readest-app/src/__tests__/utils/library-utils.test.ts

@@ -544,6 +544,18 @@ describe('getGroupSortValue', () => {
     expect(getGroupSortValue(group, LibrarySortByType.Series)).toBe('My Series');
   });
 
+  it('should return max read ratio for progress sort', () => {
+    const group = createMockGroup({
+      books: [
+        createMockBook({ progress: [10, 100] }),
+        createMockBook({ progress: [80, 100] }),
+        createMockBook({}),
+      ],
+    });
+
+    expect(getGroupSortValue(group, LibrarySortByType.Progress)).toBe(0.8);
+  });
+
   it('should handle empty groups gracefully', () => {
     const group = createMockGroup({ books: [] });