Proper UCI pipeline: filter full signal before windowing, revert norm_params to UCI body_acc

Fix gravity separation: use window mean instead of 0.3Hz LP (filter needs 167 samples to settle, window is only 128); recompute norm_params to match

Fix norm_params: 561 index-keyed entries; update loader to match

Fix normalization: recompute norm_params from physical-unit UCI raw signals; add Phyphox reset button

wire up Phyphox pipeline: full 561 feature extraction from raw CSV

working placeholder app with sample selector and phyphox tab