Add swipe-to-switch-printer and auto-navigate on tag scan
Swiping left/right on the SpoolBuddy touchscreen now cycles through
online printers instead of triggering browser back/forward navigation.
Uses touch-action: pan-y to suppress Chromium's native swipe history
gesture. Auto-navigates to dashboard when a new NFC tag is detected
on any other page, with edge detection so a persistent tag doesn't
block manual navigation. Also wakes the screen if blanked.