feat(cbz): adapt reader to real archive structure — PageIndex skips macOS junk (__MACOSX/ and ._ AppleDouble were polluting pages with 163-byte blacks), pages endpoint derives chapters[{title,start}] from folder layout, imageless zip now lands state=error instead of an empty reader, CbzReader gains 目录 sidebar + prev/next chapter (TextReader pattern, rd-* classes); pagesidx cache key bumped for one-time invalidation; e2e on 311MB 調教開關：第二季.zip: 15048→7524 real pages, 52 chapters, all JPEGs

backend/internal/bookfile/zip.go

@@ -26,6 +26,14 @@ func isImage(name string) bool {
 	return false
 }
 
+// junkEntry: macOS 打包混入的资源叉垃圾(__MACOSX/ 目录与 ._* AppleDouble),不是页
+func junkEntry(name string) bool {
+	if strings.HasPrefix(strings.ToLower(name), "__macosx/") {
+		return true
+	}
+	return strings.HasPrefix(path.Base(name), "._")
+}
+
 func PageIndex(f io.ReaderAt, size int64) ([]string, error) {
 	zr, err := zip.NewReader(f, size)
 	if err != nil {
@@ -36,6 +44,9 @@ func PageIndex(f io.ReaderAt, size int64) ([]string, error) {
 		if unsafeEntry(zf.Name) {
 			return nil, fmt.Errorf("%w: %s", ErrUnsafeZip, zf.Name)
 		}
+		if junkEntry(zf.Name) {
+			continue
+		}
 		if isImage(zf.Name) {
 			names = append(names, zf.Name)
 		}

backend/internal/bookfile/zip_test.go

@@ -38,6 +38,23 @@ func TestPageIndexSortAndFilter(t *testing.T) {
 	}
 }
 
+func TestPageIndexSkipsAppleDouble(t *testing.T) {
+	r := zipOf(t, "第2季/第2話/0001.jpg", "第2季/第1話/._0001.jpg", "__MACOSX/第2季/._0001.jpg", "第2季/第1話/0001.jpg", "._top.jpg")
+	idx, err := PageIndex(r, int64(r.Len()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []string{"第2季/第1話/0001.jpg", "第2季/第2話/0001.jpg"}
+	if len(idx) != len(want) {
+		t.Fatalf("got %v want %v", idx, want)
+	}
+	for i := range want {
+		if idx[i] != want[i] {
+			t.Fatalf("got %v want %v", idx, want)
+		}
+	}
+}
+
 func TestPageIndexRejectsSlip(t *testing.T) {
 	for _, bad := range []string{"../evil.jpg", "/etc/passwd.jpg", "a\\..\\b.jpg", "pag\ne.jpg", "pag\re.jpg"} {
 		r := zipOf(t, bad)