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/core/include/opencv2/core/operations.hpp

@@ -490,7 +490,7 @@ message in the Exception constructor.
 |`const char*`|`%s`|
 |`char`|`%c`|
 |`float` / `double`|`%f`,`%g`|
-|`int`, `long`, `long long`|`%d`, `%ld`, ``%lld`|
+|`int`, `long`, `long long`|`%d`, `%ld`, `%lld`|
 |`unsigned`, `unsigned long`, `unsigned long long`|`%u`, `%lu`, `%llu`|
 |`uint64` -> `uintmax_t`, `int64` -> `intmax_t`|`%ju`, `%jd`|
 |`size_t`|`%zu`|