feat: enforce @/ alias for imports and fix all relative parent imports (#16787)

## Summary
This PR enforces the use of `@/` alias for imports instead of relative
parent imports (`../`).

## Changes

### ESLint Configuration
- Added `no-restricted-imports` pattern in `eslint.config.react.mjs` to
block `../*` imports with the message "Relative parent imports are not
allowed. Use @/ alias instead."
- Removed the non-working `import/no-relative-parent-imports` rule
(doesn't work properly in ESLint flat config)

### VS Code Settings
- Added `javascript.preferences.importModuleSpecifier: non-relative` to
`.vscode/settings.json` (TypeScript setting was already there)

### Code Fixes
- Fixed **941 relative parent imports** across **706 files** in
`packages/twenty-front`
- All `../` imports converted to use `@/` alias

## Why
- Consistent import style across the codebase
- Easier to move files without breaking imports
- Better IDE support for auto-imports
- Clearer understanding of where imports come from

packages/twenty-front/src/modules/client-config/hooks/useClientConfig.ts

@@ -26,8 +26,8 @@ import { type ClientConfig } from '@/client-config/types/ClientConfig';
 import { domainConfigurationState } from '@/domain-manager/states/domainConfigurationState';
 import { useCallback } from 'react';
 import { useRecoilState, useSetRecoilState } from 'recoil';
-import { clientConfigApiStatusState } from '../states/clientConfigApiStatusState';
-import { getClientConfig } from '../utils/getClientConfig';
+import { clientConfigApiStatusState } from '@/client-config/states/clientConfigApiStatusState';
+import { getClientConfig } from '@/client-config/utils/getClientConfig';
 
 type UseClientConfigResult = {
   data: { clientConfig: ClientConfig } | undefined;