Merge pull request #28903 from Kumataro:supportDoxygen1_15_0

doc: modernize Doxygen comments to support for v1.15.0 #28903

This PR addresses several documentation build failures encountered with modern Doxygen versions, particularly v1.15.0 (shipped with Ubuntu 26.04).

- flann module: Updated license headers from /**** to /*M****. This prevents Doxygen from misinterpreting the license text (specifically the unclosed backticks in ``AS IS'') as documentation blocks, which previously caused "Reached end of file" errors.
- core module: Fixed a typo in operations.hpp where a doubled backtick (``) caused parsing to fail.
- tutorials: Fixed a missing backtick in real_time_pose.markdown (around line 108) and corrected typos in the RobustMatcher class name.
- Links: Resolved explicit link request failures in calib3d.hpp by ensuring proper namespace resolution.

These fixes ensure that the documentation can be generated without errors on the latest toolchains.

### 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
- [ ] 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

modules/calib3d/include/opencv2/calib3d.hpp

@@ -4171,7 +4171,7 @@ namespace fisheye
         which are dimensionless coordinates in the camera's focal plane, independent of intrinsic parameters.
 
     @note **Fisheye vs. Standard Model:**
-    Use this function (#fisheye::undistortPoints) for fisheye cameras (wide-angle lenses).
+    Use this function (#cv::fisheye::undistortPoints) for fisheye cameras (wide-angle lenses).
     For standard pinhole cameras, use #undistortPoints instead. The fisheye model uses a different distortion
     parameterization (4 coefficients) compared to the standard model (4-14 coefficients).
 
@@ -4220,14 +4220,14 @@ namespace fisheye
 
     The function transforms an image to compensate radial lens distortion.
 
-    The function is simply a combination of #fisheye::initUndistortRectifyMap (with unity R ) and #remap
+    The function is simply a combination of #cv::fisheye::initUndistortRectifyMap (with unity R ) and #remap
     (with bilinear interpolation). See the former function for details of the transformation being
     performed.
 
     See below the results of undistortImage.
        -   a\) result of undistort of perspective camera model (all possible coefficients (k_1, k_2, k_3,
             k_4, k_5, k_6) of distortion were optimized under calibration)
-        -   b\) result of #fisheye::undistortImage of fisheye camera model (all possible coefficients (k_1, k_2,
+        -   b\) result of #cv::fisheye::undistortImage of fisheye camera model (all possible coefficients (k_1, k_2,
             k_3, k_4) of fisheye distortion were optimized under calibration)
         -   c\) original image was captured with fisheye lens