Color system (#47288)

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES/NO

## What kind of change does this PR introduce?

Bug fix, feature, docs update, ...

## What is the current behavior?

Please link any relevant issues here.

## What is the new behavior?

Feel free to include screenshots if it includes visual changes.

## Additional context

Add any other context or screenshots.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Refreshed theming across the UI to use modern color expressions and
shared theme variables (including OKLCH-based gradients), improving
consistency for charts, code blocks, overlays, icons, and decorative
backgrounds.
* **Bug Fixes**
* Improved light/dark color and gradient consistency across axis/grid
styling, reference lines, buttons/badges, sidebar accents, loaders, and
other visual components.
* **Documentation**
* Updated styling/theming guidance to align with the revised semantic
token system and the updated theme variable usage patterns.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

apps/studio/components/interfaces/Functions/EdgeFunctionOverview/EdgeFunctionOverview.utils.ts

@@ -105,7 +105,7 @@ export const CPU_TIME_CHART_CONFIG = {
 export const EXECUTION_TIME_CHART_CONFIG = {
   avg_execution_time: {
     label: 'Average Execution Time',
-    color: 'hsl(var(--foreground-default))',
+    color: 'var(--foreground-default)',
   },
   max_execution_time: {
     label: 'Max Execution Time',