feat: Aligned Masking Model with Johnston (1988) and standardized configurations

[lucianodato]

Summary

This PR aligns the MaskingEstimator strictly with the Johnston (1988) psychoacoustic model while providing modern enhancements as optional toggles. It also centralizes all DSP parameters into configurations.h and updates the repository's coding standards.

Key Changes

• MaskingEstimator Refinement:
  • Strict Johnston (1988) compliance by default.
  • Added optional temporal masking (forward/backward).
  • Added adjustable spectral additivity exponent (Linear vs. PEAQ precision).
• Configuration Centralization:
  • Extracted all magic numbers from MaskingVeto, TransientDetector, and MaskingEstimator into src/shared/configurations.h.
• Coding Standards:
  • Updated the coding_standards skill to mandate "No Magic Numbers in Core DSP".
• Bug Fix:
  • Fixed a missing transient_detector_process call in MaskingVeto.

Verification Status

• All unit tests for masking_estimator, masking_veto, and transient_detector are passing.
• Clean build and installation verified.

[codecov]

Codecov Report

❌ Patch coverage is 86.86441% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.25%. Comparing base (0fbc3c1) to head (65da3cc).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/shared/utils/spectral_smoother.c	79.54%	4 Missing and 5 partials ⚠️
...rc/shared/denoiser_logic/processing/masking_veto.c	82.60%	1 Missing and 7 partials ⚠️
src/shared/utils/masking_estimator.c	92.59%	0 Missing and 8 partials ⚠️
src/shared/utils/transient_detector.c	86.66%	1 Missing and 3 partials ⚠️
src/processors/denoiser/spectral_denoiser.c	75.00%	0 Missing and 1 partial ⚠️
src/processors/denoiser2d/spectral_2d_denoiser.c	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
- Coverage   77.29%   77.25%   -0.04%     
==========================================
  Files          33       33              
  Lines        2911     3012     +101     
  Branches      640      666      +26     
==========================================
+ Hits         2250     2327      +77     
- Misses        345      364      +19     
- Partials      316      321       +5     

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