Fixes position of red rectangle on top of zbar codes and fixes screen area...

Fixes position of red rectangle on top of zbar codes and fixes screen area where touch activates zbar's data-related menu

Fixes issue #50

Tests done on my PP 3GB with Megapixels 1.5.2 on Mobian bookworm with Phosh:

PP in portrait position

preview 360x640

size 720x1280

scale 2.0

tappable area roughly x=0-360 y=50-580

top bar height 44px , bottom bar height 72px

(preview height - bars' height = 640 - 44 - 72 = 524 approx.= 530 = y_range)

no bar on left/right, then zbar_x=x

zbar_y is corrected for top bar's height

PP in landscape position

preview 640x360

size 1024x576

scale 1.6

tappable area roughly x=40-660 y=0-285

bars both on left and right side, zbar_x is adjusted according to left bar width

zbar_y=y mapping is not perfect, active area is moved a bit down with respect to red preview area, but this MR is anyway a huge improvement over actual situation