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/spreadsheet-import/steps/components/ValidationStep/components/columns.tsx

@@ -14,7 +14,7 @@ import camelCase from 'lodash.camelcase';
 import { isDefined } from 'twenty-shared/utils';
 import { AppTooltip, TooltipDelay } from 'twenty-ui/display';
 import { Checkbox, CheckboxVariant, Toggle } from 'twenty-ui/input';
-import { type ImportedStructuredRowMetadata } from '../types';
+import { type ImportedStructuredRowMetadata } from '@/spreadsheet-import/steps/components/ValidationStep/types';
 
 const StyledHeaderContainer = styled.div`
   align-items: center;

packages/twenty-front/src/modules/spreadsheet-import/steps/components/__stories__/Steps.stories.tsx

@@ -6,7 +6,7 @@ import { stepBarInternalState } from '@/ui/navigation/step-bar/states/stepBarInt
 import { ContextStoreDecorator } from '~/testing/decorators/ContextStoreDecorator';
 import { I18nFrontDecorator } from '~/testing/decorators/I18nFrontDecorator';
 import { ObjectMetadataItemsDecorator } from '~/testing/decorators/ObjectMetadataItemsDecorator';
-import { SpreadsheetImportStepperContainer } from '../SpreadsheetImportStepperContainer';
+import { SpreadsheetImportStepperContainer } from '@/spreadsheet-import/steps/components/SpreadsheetImportStepperContainer';
 
 const meta: Meta<typeof SpreadsheetImportStepperContainer> = {
   title: 'Modules/SpreadsheetImport/Steps',