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-ui/src/input/button/components/LightIconButton.tsx

@@ -1,7 +1,7 @@
 import { styled } from '@linaria/react';
 import { type IconComponent } from '@ui/display';
-import { ICON_SIZES, themeCssVariables } from '@ui/theme-constants';
-import { type ComponentProps, type MouseEvent } from 'react';
+import { ThemeContext, themeCssVariables } from '@ui/theme-constants';
+import { type ComponentProps, type MouseEvent, useContext } from 'react';
 
 export type LightIconButtonAccent = 'secondary' | 'tertiary';
 export type LightIconButtonSize = 'small' | 'medium';
@@ -105,6 +105,8 @@ export const LightIconButton = ({
   onClick,
   title,
 }: LightIconButtonProps) => {
+  const { theme } = useContext(ThemeContext);
+
   return (
     <StyledButton
       data-testid={testId}
@@ -119,7 +121,9 @@ export const LightIconButton = ({
       title={title}
     >
       {Icon && (
-        <Icon size={size === 'medium' ? ICON_SIZES.md : ICON_SIZES.sm} />
+        <Icon
+          size={size === 'medium' ? theme.icon.size.md : theme.icon.size.sm}
+        />
       )}
     </StyledButton>
   );