[FAB-118] Fix canvas fit on mobile screen

[nicolauscg]

behavior after bug fixes FAB-116, FAB-117, FAB-118

• translation scaling is dynamic, so drawing after resizing screen will be correct
• drawing session screen not scrollable in small screens
• canvas contained in small screen
• when screen is short and wide, no white background below screen before drawing session (fixed by adding overflow-y-hidden when invisible)
• canvas height can now shrink when screen/canvas width stays constant

Todo

• canvas always fit screen, even on mobile
• resizing only screen height will correctly adjust canvas dimension
• dynamically adjust scaling factor for canvas translation when screen is resized