Add EEG band power features (alpha, beta, etc.)

[baris-talar]

Goal

Add biologically meaningful EEG features based on frequency bands.

Target Bands

• Delta (0.5–4 Hz)
• Theta (4–8 Hz)
• Alpha (8–13 Hz)
• Beta (13–30 Hz)

Tasks

• Implement bandpass filters or FFT-based band extraction
• Compute power for each band per channel
• Integrate into features.py
• Append to existing feature vector
• Ensure pipeline compatibility (calibrate → train → predict)

Why this matters

Band power is one of the most standard and informative EEG features and is widely used in neuroscience and BCI systems.

Acceptance Criteria

• Band power features correctly computed
• Features integrated cleanly into pipeline
• No breaking changes to existing workflow

Final Step

• Update README to explain band power features and how they improve the model