feat(backend): book list/detail/delete with embedded progress + cache cleanup

backend/internal/api/libraries_test.go

@@ -12,9 +12,10 @@ import (
 )
 
 func TestLibraryCreateListUpload(t *testing.T) {
-	_, h := setupAPI(t)
+	_, _, h, booksDir := setupAPI(t)
 	tok := adminToken(t, h)
-	root := t.TempDir()
+	root := filepath.Join(booksDir, "lib1") // 必须落在解析过软链的 booksDir 内
+	os.MkdirAll(root, 0o755)
 	w := do(h, "POST", "/api/libraries", tok, map[string]string{"name": "comics", "root_path": root})
 	if w.Code != 201 {
 		t.Fatalf("create lib %d %s", w.Code, w.Body)