Merge pull request #26412 from Kumataro:fix26411

doc: update to doxygen-awesome-css v2.3.4 #26412

Close https://github.com/opencv/opencv/issues/26411

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [X] The PR is proposed to the proper branch
- [X] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

doc/Doxyfile.in

@@ -157,7 +157,7 @@ HTML_FILE_EXTENSION    = .html
 HTML_HEADER            = @CMAKE_CURRENT_SOURCE_DIR@/header.html
 HTML_FOOTER            = @CMAKE_CURRENT_SOURCE_DIR@/footer.html
 HTML_STYLESHEET        =
-HTML_EXTRA_STYLESHEET  = @CMAKE_CURRENT_SOURCE_DIR@/doxygen-awesome.css
+HTML_EXTRA_STYLESHEET  = @CMAKE_CURRENT_SOURCE_DIR@/doxygen-awesome.css @CMAKE_CURRENT_SOURCE_DIR@/custom.css
 HTML_EXTRA_FILES       = @CMAKE_DOXYGEN_HTML_FILES@
 HTML_COLORSTYLE        = LIGHT
 HTML_COLORSTYLE_HUE    = 220

doc/custom.css

@@ -0,0 +1,14 @@
+/*
+ * To narrow the separator height for class members.
+ */
+td.memSeparator {
+    display: none !important;
+}
+
+/*
+ * With Doxygen 1.9.8, some page contents are hidden by the ToC after scrolling.
+ * To workaround, ToC position is changed to"relative".
+ */
+div.toc {
+    position: relative !important;
+}