[4.x] A fresh coat of paint

[jessarcher]

This PR freshens up Telescope with new colors, icons, fonts, shadows, sizing, spacing, and alignment.

There are numerous other minor tweaks, including:

• Hover states for the sidebar.
• Right-aligning numeric values in tables.
• Adding an icon to the search field.
• Preventing the table heading height from jumping around as you switch between screens.
• Fixing various places where rounded corners were covered by a square element with a background color.
• More consistent usage of badges

Day mode

Index screen

Before

After

Preview screen

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After

Night mode

Index screen

Before

After

Preview screen

Before

After

[taylorotwell]

[jtomek]

I have no words. This is so refreshing. Thank you!