test: add SEL103 ECG extracted feature validation against WFDB annotations**
- Add SEL103 extracted feature validation test covering P, QRS, and T waves
- Match detected beats against WFDB reference annotations using R-peak alignment
- Compare algorithm wave boundaries and durations against WFDB ground truth with tolerances
- Validate P, R, and T wave amplitudes against the baseline-corrected ECG signal
- Generate CSV output containing raw, processed, WFDB, and algorithm annotations
- Add waveform annotation labeling for P, QRS, and T waves