chore(twenty-front): migrate small modules from Emotion to Linaria (PR 1/10) (#18314)

## Emotion → Linaria migration — PR 1 of 10

First batch of the `twenty-front` migration from Emotion (runtime
CSS-in-JS) to Linaria (zero-runtime, build-time extraction via
wyw-in-js). Covers **100 files** across 10 small standalone modules —
chosen as the lowest-risk starting point.

### Modules migrated

spreadsheet-import (28) · navigation-menu-item (17) · views (14) ·
billing (10) · blocknote-editor (7) · advanced-text-editor (7) ·
favorites (7) · navigation (4) · information-banner (3) ·
sign-in-background-mock (3)

### Migration pattern

Every file follows the same mechanical transformation:

| Emotion | Linaria |
|---|---|
| `import styled from '@emotion/styled'` | `import { styled } from
'@linaria/react'` |
| `${({ theme }) => theme.font.color.primary}` |
`${themeCssVariables.font.color.primary}` |
| `${({ theme }) => theme.spacing(4)}` |
`${themeCssVariables.spacing[4]}` |
| `const theme = useTheme()` | `const { theme } =
useContext(ThemeContext)` |
| `import { type Theme } from '@emotion/react'` | `import { type
ThemeType } from 'twenty-ui/theme'` |

`themeCssVariables` is a build-time object where every leaf is a
`var(--t-xxx)` CSS custom property reference, evaluated statically by
wyw-in-js. Runtime theme access (icon sizes, colors passed as props)
uses `useContext(ThemeContext)`.

### Gotchas encountered & fixed

- **Interpolation return types** — wyw-in-js requires `string | number`,
never `false`/`undefined`. Replaced `condition && 'css'` with `condition
? 'css' : ''`.
- **`css` tag inside `styled` templates** — Linaria `css` returns a
class name, not CSS text. Replaced with plain template strings.
- **`styled(Component)` needs `className`** — added `className` prop to
`NavigationDrawerSection`, `DropdownMenuItemsContainer`, and `Heading`.
- **`shouldForwardProp` not supported** — Linaria filters invalid DOM
props automatically for HTML elements. For custom components, used
wrapper divs where needed.
- **`FormFieldPlaceholderStyles`** — converted from Emotion `css`
function to a static string using `themeCssVariables`.

packages/twenty-ui/src/json-visualizer/components/JsonNestedNode.tsx

@@ -7,7 +7,8 @@ import { JsonNodeValue } from '@ui/json-visualizer/components/internal/JsonNodeV
 import { JsonNode } from '@ui/json-visualizer/components/JsonNode';
 import { useJsonTreeContextOrThrow } from '@ui/json-visualizer/hooks/useJsonTreeContextOrThrow';
 import { type JsonNodeHighlighting } from '@ui/json-visualizer/types/JsonNodeHighlighting';
-import { ANIMATION, themeCssVariables } from '@ui/theme';
+import { ANIMATION } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 import { AnimatePresence, motion } from 'framer-motion';
 import { useState } from 'react';
 import { isDefined } from 'twenty-shared/utils';

packages/twenty-ui/src/json-visualizer/components/JsonValueNode.tsx

@@ -4,7 +4,7 @@ import { JsonListItem } from '@ui/json-visualizer/components/internal/JsonListIt
 import { JsonNodeLabel } from '@ui/json-visualizer/components/internal/JsonNodeLabel';
 import { JsonNodeValue } from '@ui/json-visualizer/components/internal/JsonNodeValue';
 import { type JsonNodeHighlighting } from '@ui/json-visualizer/types/JsonNodeHighlighting';
-import { themeCssVariables } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 
 const StyledListItem = styled(JsonListItem)`
   column-gap: ${themeCssVariables.spacing[2]};

packages/twenty-ui/src/json-visualizer/components/internal/JsonArrow.tsx

@@ -2,7 +2,8 @@ import { styled } from '@linaria/react';
 import { VisibilityHidden } from '@ui/accessibility';
 import { IconChevronDown } from '@ui/display';
 import { useJsonTreeContextOrThrow } from '@ui/json-visualizer/hooks/useJsonTreeContextOrThrow';
-import { ANIMATION, ThemeContext, themeCssVariables } from '@ui/theme';
+import { ANIMATION, ThemeContext } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 import { motion } from 'framer-motion';
 import { useContext } from 'react';
 

packages/twenty-ui/src/json-visualizer/components/internal/JsonList.tsx

@@ -1,5 +1,5 @@
 import { styled } from '@linaria/react';
-import { themeCssVariables } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 
 const StyledList = styled.ul<{ depth: number }>`
   margin: 0;

packages/twenty-ui/src/json-visualizer/components/internal/JsonNodeLabel.tsx

@@ -1,7 +1,8 @@
 import { styled } from '@linaria/react';
 import { type IconComponent } from '@ui/display';
 import { type JsonNodeHighlighting } from '@ui/json-visualizer/types/JsonNodeHighlighting';
-import { ThemeContext, themeCssVariables } from '@ui/theme';
+import { ThemeContext } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 import { useContext } from 'react';
 
 const StyledLabelContainer = styled.span<{

packages/twenty-ui/src/json-visualizer/components/internal/JsonNodeValue.tsx

@@ -1,7 +1,7 @@
 import { styled } from '@linaria/react';
 import { useJsonTreeContextOrThrow } from '@ui/json-visualizer/hooks/useJsonTreeContextOrThrow';
 import { type JsonNodeHighlighting } from '@ui/json-visualizer/types/JsonNodeHighlighting';
-import { themeCssVariables } from '@ui/theme';
+import { themeCssVariables } from '@ui/theme-constants';
 
 const StyledText = styled.span<{
   highlighting: JsonNodeHighlighting | undefined;