feat: extend AudioFeatures dataclass with additional spectral and temporal metrics

app/services/feature_extractor.py

@@ -41,15 +41,35 @@ class AudioFeatures:
     duration_sec: float
     sample_rate: int
     rms_energy: float
+    rms_std: float
     tempo_bpm: float
     tempo_stability: float      # std of inter-beat intervals
+    tempo_cv: float             # coefficient of variation of beat intervals
     spectral_centroid_mean: float
     spectral_centroid_std: float
     spectral_flatness_mean: float
+    spectral_flatness_std: float
+    spectral_bandwidth_mean: float
+    spectral_bandwidth_std: float
+    spectral_rolloff_mean: float
+    spectral_rolloff_std: float
+    spectral_contrast_mean: float
+    spectral_contrast_std: float
     mfcc_variance: float        # mean variance across MFCC bands
+    mfcc_delta_var: float       # mean variance of MFCC first derivative
+    mfcc_delta2_var: float      # mean variance of MFCC second derivative
     chroma_entropy: float       # entropy of chroma distribution
+    chroma_std: float           # temporal chroma variability
+    chroma_transition_rate: float  # pitch class change rate
     harmonic_ratio: float       # harmonic / (harmonic + percussive)
+    tonnetz_std: float          # tonal centroid variability
     zero_crossing_rate: float
+    zero_crossing_std: float
+    onset_strength_mean: float
+    onset_strength_std: float
+    rms_dynamic_range: float
+    beat_count: int
+    mel_flatness: float
 
 
 @dataclass