Deprecate runtime theme objects in favor of CSS variables (#18402)

## Summary

- **Eliminate `ICON_SIZES` / `ICON_STROKES` constants**: all icon
dimensions are now resolved at runtime via
`resolveThemeVariableAsNumber(themeCssVariables.icon.size.X)`, ensuring
values always come from computed CSS variables
- **No more consumer imports from `twenty-ui/theme`**: moved
`ColorSchemeContext`, `ColorSchemeProvider`, `ThemeColor`,
`MAIN_COLOR_NAMES`, `getNextThemeColor`, `AnimationDuration` to
`twenty-ui/theme-constants`
- **Remove `ThemeContext` / `ThemeContextProvider` / `ThemeProvider` /
`ThemeType`**: replaced across ~300 files with `themeCssVariables` (for
CSS contexts) or `resolveThemeVariable` / `resolveThemeVariableAsNumber`
(for JS runtime values)
- **Simplify provider chain**: only `ColorSchemeProvider` remains — it
toggles `light`/`dark` class on `document.documentElement` and provides
`colorScheme` via React context
- **Fix pre-existing test failures**: `useIcons.test.ts`
(non-configurable ES module spy) and
`turnRecordFilterGroupIntoGqlOperationFilter.test.ts`
(`Omit<RecordFilter, 'id'>` type mismatch)

### Theme access pattern (before → after)

| Context | Before | After |
|---------|--------|-------|
| CSS (Linaria) | `${({ theme }) => theme.font.color.primary}` |
`${themeCssVariables.font.color.primary}` |
| JS runtime (icon size, animation) | `theme.icon.size.md` /
`ICON_SIZES.md` |
`resolveThemeVariableAsNumber(themeCssVariables.icon.size.md)` |
| Color scheme check | `theme.name === 'dark'` |
`useContext(ColorSchemeContext).colorScheme === 'dark'` |

packages/twenty-front/src/loading/components/LeftPanelSkeletonLoader.tsx

@@ -5,9 +5,9 @@ import Skeleton, { SkeletonTheme } from 'react-loading-skeleton';
 import { SKELETON_LOADER_HEIGHT_SIZES } from '@/activities/components/SkeletonLoader';
 import { NAVIGATION_DRAWER_CONSTRAINTS } from '@/ui/layout/resizable-panel/constants/NavigationDrawerConstraints';
 import { useIsMobile } from '@/ui/utilities/responsive/hooks/useIsMobile';
-import { useContext } from 'react';
-import { ANIMATION, ThemeContext } from 'twenty-ui/theme';
 import { MainNavigationDrawerItemsSkeletonLoader } from '~/loading/components/MainNavigationDrawerItemsSkeletonLoader';
+import { useContext } from 'react';
+import { ThemeContext } from 'twenty-ui/theme-constants';
 
 const StyledAnimatedContainer = styled(motion.div)`
   align-items: center;
@@ -47,9 +47,8 @@ const StyledSkeletonTitleContainer = styled.div`
 `;
 
 export const LeftPanelSkeletonLoader = () => {
-  const isMobile = useIsMobile();
   const { theme } = useContext(ThemeContext);
-
+  const isMobile = useIsMobile();
   return (
     <StyledAnimatedContainer
       initial={false}
@@ -57,7 +56,9 @@ export const LeftPanelSkeletonLoader = () => {
         width: isMobile ? 0 : NAVIGATION_DRAWER_CONSTRAINTS.default,
         opacity: isMobile ? 0 : 1,
       }}
-      transition={{ duration: ANIMATION.duration.fast }}
+      transition={{
+        duration: theme.animation.duration.fast,
+      }}
     >
       <StyledItemsContainer>
         <StyledSkeletonTitleContainer>