Make the new editor look nice

Is your feature request related to a problem? Please describe.
Make the editor looks nice.

• Icons should be monochrome svg scaled to the size of 16x16. this could be configurable.
• Slightly round corners for non panel controls, this could be configurable.
• Keep it compact with a font size of 8-13 and a margin of 3 on all sides, this could be configurable.
• Use classic desktop widgets for desktop, aka no modern mobile or web pages. aka more like dear imgui, unity3d, godot, unreal. this could be different on mobile.
• Allow modifying the editor color and contrast.
• The ability to switch between light and dark mode with icons.
• Use a constant height for controls that are not containers
• Icons should be centered vertically and horizontally not filled
• Icon Buttons should be small with the same width as height

Describe the solution you'd like
See above.

Describe alternatives you've considered
Too many to count.

Additional context
A nice looking editor is going to attract people to your engine.
This is because people prefer fashion over functionality in their hearts.

No files, entry points, or tests are named. Start by locating the editor UI subsystem and determine which of the requested visual changes belong in a focused contribution. Done requires an agreed scope and reviewable criteria for the selected styling, sizing, icon, and theme behavior.