Remove CSS modules (#6017)

CSS modules were used as a first test for performance optimization.

We later found out that Linaria was a better tradeoff.

This PR removes what was implemented in CSS modules and also the CSS
theme file that was created that was overlapping with the TS theme
files.

packages/twenty-ui/src/theme/provider/ThemeProvider.tsx

@@ -1,23 +1,16 @@
-import { ReactNode, useEffect } from 'react';
+import { ReactNode } from 'react';
 import { ThemeProvider as EmotionThemeProvider } from '@emotion/react';
 
 import { ThemeContextProvider } from '@ui/theme/provider/ThemeContextProvider';
 
 import { ThemeType } from '..';
 
-import './theme.css';
-
 type ThemeProviderProps = {
   theme: ThemeType;
   children: ReactNode;
 };
 
 const ThemeProvider = ({ theme, children }: ThemeProviderProps) => {
-  useEffect(() => {
-    document.documentElement.className =
-      theme.name === 'dark' ? 'dark' : 'light';
-  }, [theme]);
-
   return (
     <EmotionThemeProvider theme={theme}>
       <ThemeContextProvider theme={theme}>{children}</ThemeContextProvider>