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/ai/components/RoutingDebugDisplay.tsx

@@ -4,8 +4,7 @@ import { useContext, useState } from 'react';
 import { IconChevronDown, IconChevronUp } from 'twenty-ui/display';
 import { JsonTree } from 'twenty-ui/json-visualizer';
 import { AnimatedExpandableContainer } from 'twenty-ui/layout';
-import { ThemeContext } from 'twenty-ui/theme';
-import { themeCssVariables } from 'twenty-ui/theme-constants';
+import { ThemeContext, themeCssVariables } from 'twenty-ui/theme-constants';
 
 import { useLingui } from '@lingui/react/macro';
 import { type DataMessagePart } from 'twenty-shared/ai';
@@ -323,8 +322,8 @@ type RoutingDebugDisplayProps = {
 };
 
 export const RoutingDebugDisplay = ({ debug }: RoutingDebugDisplayProps) => {
-  const { t } = useLingui();
   const { theme } = useContext(ThemeContext);
+  const { t } = useLingui();
   const { copyToClipboard } = useCopyToClipboard();
   const [isExpanded, setIsExpanded] = useState(false);
   const [activeTab, setActiveTab] = useState<TabType>('timing');