Add built-in white and black themes

internal/api/themes_test.go

@@ -29,9 +29,15 @@ func TestThemeAndShareAppearanceBoundaries(t *testing.T) {
 		t.Fatalf("匿名用户不应读取主题，得到 %d", code)
 	}
 	themes := decode[struct{ Themes []themeManifest }](t, f.do(f.admin, "GET", "/api/v1/themes", "", nil))
-	if len(themes.Themes) != 2 || themes.Themes[1].ID != "paper" {
+	if len(themes.Themes) != 4 || themes.Themes[0].ID != "default" || themes.Themes[1].ID != "white" || themes.Themes[2].ID != "black" || themes.Themes[3].ID != "paper" {
 		t.Fatalf("主题列表错误：%+v", themes.Themes)
 	}
+	for _, id := range []string{"white", "black"} {
+		theme := decode[map[string]string](t, f.do(f.admin, "GET", "/api/v1/themes/"+id, "", nil))
+		if theme["id"] != id || !strings.Contains(theme["css"], "--rm-bg:") {
+			t.Fatalf("内置主题未提供配色：%s", id)
+		}
+	}
 	theme := decode[map[string]string](t, f.do(f.admin, "GET", "/api/v1/themes/paper", "", nil))
 	if !strings.Contains(theme["css"], "#faf6ed") {
 		t.Fatal("未读取到主题 CSS")