Inconsistent signal_interpolate methods in ppg_quality()

[athatcher13]

Describe the bug
ppg_quality with method=

• 'templatematch': _ppg_quality_templatematch() uses signal_interpolate with method='quadratic'
• 'disimilarity': _ppg_quality_disimilarity() uses signal_interpolate with method='previous'

Expected behaviour
I would expect this behavior to be consistent between ppg_quality methods. method='previous' seems most apt as the quality is truly calcuated beat-by-beat - it will hold the most recent beat's quality value until a new value comes along to replace it. method='quadratic' frequently fills the vector with values above and below the specified 'templatematch' range of [0, 1].

System Specifications

• OS: Windows (WindowsPE 64bit)
• Python: 3.11.9
• NeuroKit2: 0.2.10
• NumPy: 2.1.2
• Pandas: 2.2.3
• SciPy: 1.14.1
• sklearn: 1.5.2
• matplotlib: 3.9.2

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