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/page-layout/components/PageLayoutGridResizeHandle.tsx

@@ -7,9 +7,7 @@ import {
   IconRadiusTopRight,
 } from 'twenty-ui/display';
 import { ResizeHandle } from 'twenty-ui/layout';
-import { themeCssVariables } from 'twenty-ui/theme-constants';
-import { ThemeContext } from 'twenty-ui/theme';
-
+import { themeCssVariables, ThemeContext } from 'twenty-ui/theme-constants';
 type WidgetHandleAxis = 'n' | 's' | 'e' | 'w' | 'ne' | 'nw' | 'se' | 'sw';
 type WidgetHorizontalHandleAxis = 'n' | 's';
 type WidgetVerticalHandleAxis = 'e' | 'w';

packages/twenty-front/src/modules/page-layout/components/PageLayoutTabListReorderableOverflowDropdown.tsx

@@ -29,7 +29,7 @@ import { useSetAtomComponentState } from '@/ui/utilities/state/jotai/hooks/useSe
 import { useContext } from 'react';
 import { CommandMenuPages } from 'twenty-shared/types';
 import { type PageLayoutType } from '~/generated-metadata/graphql';
-import { ThemeContext } from 'twenty-ui/theme';
+import { ThemeContext } from 'twenty-ui/theme-constants';
 
 const StyledOverflowDropdownListDraggableWrapper = styled.div`
   display: flex;

packages/twenty-front/src/modules/page-layout/components/PageLayoutTabMenuItemSelectAvatar.tsx

@@ -11,9 +11,7 @@ import {
   StyledMenuItemLabel,
   StyledMenuItemLeftContent,
 } from 'twenty-ui/navigation';
-import { themeCssVariables } from 'twenty-ui/theme-constants';
-import { ThemeContext } from 'twenty-ui/theme';
-
+import { themeCssVariables, ThemeContext } from 'twenty-ui/theme-constants';
 const StyledTextContainer = styled.div`
   display: flex;
   align-items: center;

packages/twenty-front/src/modules/page-layout/components/PageLayoutTabRenderClone.tsx

@@ -8,9 +8,8 @@ import { styled } from '@linaria/react';
 import { type DraggableProvided } from '@hello-pangea/dnd';
 import { StyledTabContainer, TabContent } from 'twenty-ui/input';
 import { MenuItemSelectAvatar } from 'twenty-ui/navigation';
+import { ThemeContext } from 'twenty-ui/theme-constants';
 import { useContext } from 'react';
-import { ThemeContext } from 'twenty-ui/theme';
-
 const StyledDraggableWrapper = styled.div`
   display: flex;
   cursor: grab;
@@ -30,7 +29,6 @@ export const PageLayoutTabRenderClone = ({
   activeTabId: string | null;
 }) => {
   const { theme } = useContext(ThemeContext);
-
   const pageLayoutTabListCurrentDragDroppableId = useAtomComponentStateValue(
     pageLayoutTabListCurrentDragDroppableIdComponentState,
   );