Merge pull request #29455 from anushkagupta200615-jpg:fix-issue-29452

Fix #29452: Remove <complex.h> to prevent _Complex macro conflicts #29455

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- [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
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- [x] There is a reference to the original bug report and related work
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      Patch to opencv_extra has the same branch name.
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---

**Description:**
Resolves https://github.com/opencv/opencv/issues/29452

**Reason for the issue:**
The C99 `<complex.h>` header defines the macro `complex` on some platforms (like NetBSD with GCC 14). Because it was included before C++ `<complex>`, this caused conflicts where `std::complex<T>` was being expanded into `std::_Complex<T>`, resulting in the reported syntax errors.

**Changes made:**
- Removed the unnecessary C-style `#include <complex.h>`.
- Added a safety guard to `#undef complex` in case any transitive lapack headers attempt to define it, ensuring `std::complex` works cleanly without C-preprocessor interference.

modules/core/src/hal_internal.cpp

@@ -47,7 +47,6 @@
 
 #ifdef HAVE_LAPACK
 
-#include <complex.h>
 #include "opencv_lapack.h"
 
 #include <cmath>