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/utils/array/__tests__/getIndexNeighboursElementsFromArray.test.ts

@@ -1,5 +1,5 @@
 import { type EachTestingContext } from 'twenty-shared/testing';
-import { getIndexNeighboursElementsFromArray } from '../getIndexNeighboursElementsFromArray';
+import { getIndexNeighboursElementsFromArray } from '~/utils/array/getIndexNeighboursElementsFromArray';
 
 type TestCase = {
   expected: ReturnType<typeof getIndexNeighboursElementsFromArray>;

packages/twenty-front/src/utils/array/__tests__/groupArrayItemsBy.test.ts

@@ -1,4 +1,4 @@
-import { groupArrayItemsBy } from '../groupArrayItemsBy';
+import { groupArrayItemsBy } from '~/utils/array/groupArrayItemsBy';
 
 describe('groupArrayItemsBy', () => {
   it('groups an array of objects by a computed key', () => {

packages/twenty-front/src/utils/array/__tests__/toSpliced.test.ts

@@ -1,4 +1,4 @@
-import { toSpliced } from '../toSpliced';
+import { toSpliced } from '~/utils/array/toSpliced';
 
 describe('toSpliced', () => {
   it('removes elements from the array starting at the given index', () => {