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/components/SearchInput.tsx

@@ -1,8 +1,7 @@
 import { styled } from '@linaria/react';
 import { IconFilter, IconSearch } from '@ui/display';
 import { IconButton } from '@ui/input/button/components/IconButton';
-import { ThemeContext } from '@ui/theme';
-import { themeCssVariables } from '@ui/theme-constants';
+import { ThemeContext, themeCssVariables } from '@ui/theme-constants';
 import { type ChangeEvent, type ReactNode, useContext, useState } from 'react';
 
 export type SearchInputProps = {

packages/twenty-ui/src/input/components/__stories__/Toggle.stories.tsx

@@ -4,7 +4,7 @@ import {
   type CatalogStory,
   ComponentDecorator,
 } from '@ui/testing';
-import { MAIN_COLORS_LIGHT } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 import { useState } from 'react';
 
 import { Toggle, type ToggleSize } from '../Toggle';
@@ -88,7 +88,7 @@ export const Catalog: CatalogStory<Story, typeof InteractiveToggle> = {
             if (color === 'default') {
               return {};
             }
-            return { color: MAIN_COLORS_LIGHT.yellow };
+            return { color: themeCssVariables.color.yellow };
           },
         },
       ],