UI/UX Improvements

[gboeker]

• pause the animation when timer is paused
• add shadow (or something else) to make the white numbers pop out from the plate during break
• only have the tomato during the first start, after clicking reset it shouldn't go back to the tomato
• transition between animations seems abrupt, not sure how to fix but maybe a sound or fade (or other visual transition)
• add sound effects when clicking button
• add sound effects when timer is complete
• when logging in, nav bar should disappear
• resize page shouldn't break to tomato