Update colors of navigation bar and tab bars

[martindsq]

Closes #1059

• Update color of the navigation bar
• Update color of the search bar
• Update color of the tab bar
• Remove unused colors
• Update tab bar icons

[mplorentz]

Let's SHIP IT 🚢 ! This makes it feel like a whole new app (even though we still have a few more places to update colors)

[mplorentz]

I think we shouldn't close #1059 right after merging this though. Some places I noticed we still need new colors:

• Settings
• Notifications tab still uses purple accent
• Your Network tab still uses purple accent
• Thread view has wrong background color in light mode.
• New Post screen

[martindsq]

I think we shouldn't close #1059 right after merging this though. Some places I noticed we still need new colors:

* Settings

* Notifications tab still uses purple accent

* Your Network tab still uses purple accent

* Thread view has wrong background color in light mode.

* New Post screen

The intent behing that issue was what I did, quickly update the navigation bar colors so that they use the new colors we have been using in swiftui. If you are ok with this, I'll close that issue after merging this one, but I'm creating a new issue that a checklist (I'd add the left menu as well that still has the purple)

[martindsq]

I created this other issue for that: #1099