make search results take up full width, less spacing

Created by: sqs

This increases the info density of search results, which is a common user request. It also makes the UI look a lot cleaner and have less dead space.

• The left/right margins are unnecessary and severely limit readability on small screens.
• The vertical spacing between search result containers is unnecessary.
• The loading indicator actually needed more margin to the top. This is slightly unrelated, but worth doing and not too different to merit a different commit.

Before (the margins take up a lot of space, esp. on narrow screens)

After