Update search.py module

[fcotizelati]

Added new functions to adaptively determine the optimal harmonic order using the H-test statistic, following the method by Xie et al. 2025:

-adaptive_optimal_harmonic_order function to compute the optimal number of harmonics. -adjust_bin_phases function to refine phase values via a polynomial (linear) fit to improve phase adjustment for folded profiles. -improved_z_n_binned function to compute the improved Zn,bin2 statistic based on adjusted phases. -z_n_search_adaptive to integrate these new functions.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 8.00000% with 46 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 79.46%. Comparing base (a91c031) to head (8ffc2db). :warning: Report is 98 commits behind head on main.

Files with missing lines	Patch %	Lines
stingray/pulse/search.py	8.00%	46 Missing :warning:

:exclamation: There is a different number of reports uploaded between BASE (a91c031) and HEAD (8ffc2db). Click for more details.

HEAD has 58 uploads less than BASE

Flag	BASE (a91c031)	HEAD (8ffc2db)
	62	4

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #904       +/-   ##
===========================================
- Coverage   96.03%   79.46%   -16.58%     
===========================================
  Files          48       48               
  Lines        9770     9820       +50     
===========================================
- Hits         9383     7803     -1580     
- Misses        387     2017     +1630     

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[matteobachetti]

@fcotizelati I'm sorry, I just realized I completely forgot to review this. Do you wish to reopen?