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/modules/settings/data-model/components/SettingsDataModelNewFieldBreadcrumbDropDown.tsx

@@ -4,16 +4,15 @@ import { DropdownContent } from '@/ui/layout/dropdown/components/DropdownContent
 import { DropdownMenuItemsContainer } from '@/ui/layout/dropdown/components/DropdownMenuItemsContainer';
 import { useCloseDropdown } from '@/ui/layout/dropdown/hooks/useCloseDropdown';
 import { styled } from '@linaria/react';
-import { t } from '@lingui/core/macro';
 import { useContext } from 'react';
+import { t } from '@lingui/core/macro';
 import { useLocation, useParams, useSearchParams } from 'react-router-dom';
 import { SettingsPath } from 'twenty-shared/types';
 import { isDefined } from 'twenty-shared/utils';
 import { IconChevronDown } from 'twenty-ui/display';
 import { Button } from 'twenty-ui/input';
 import { MenuItem } from 'twenty-ui/navigation';
-import { ThemeContext } from 'twenty-ui/theme';
-import { themeCssVariables } from 'twenty-ui/theme-constants';
+import { ThemeContext, themeCssVariables } from 'twenty-ui/theme-constants';
 import { useNavigateSettings } from '~/hooks/useNavigateSettings';
 
 const StyledContainer = styled.div`
@@ -52,13 +51,13 @@ const StyledButton = styled(Button)`
 `;
 
 export const SettingsDataModelNewFieldBreadcrumbDropDown = () => {
+  const { theme } = useContext(ThemeContext);
   const dropdownId = `settings-object-new-field-breadcrumb-dropdown`;
   const { closeDropdown } = useCloseDropdown();
   const navigate = useNavigateSettings();
   const location = useLocation();
   const { objectNamePlural = '' } = useParams();
   const [searchParams] = useSearchParams();
-  const { theme } = useContext(ThemeContext);
 
   const fieldType = searchParams.get('fieldType') as SettingsFieldType;
   const isConfigureStep = location.pathname.includes('/configure');