Migrate from ESLint to OxLint (#18443)

## Summary

Fully replaces ESLint with OxLint across the entire monorepo:

- **Replaced all ESLint configs** (`eslint.config.mjs`) with OxLint
configs (`.oxlintrc.json`) for every package: `twenty-front`,
`twenty-server`, `twenty-emails`, `twenty-ui`, `twenty-shared`,
`twenty-sdk`, `twenty-zapier`, `twenty-docs`, `twenty-website`,
`twenty-apps/*`, `create-twenty-app`
- **Migrated custom lint rules** from ESLint plugin format to OxLint JS
plugin system (`@oxlint/plugins`), including
`styled-components-prefixed-with-styled`, `no-hardcoded-colors`,
`sort-css-properties-alphabetically`,
`graphql-resolvers-should-be-guarded`,
`rest-api-methods-should-be-guarded`, `max-consts-per-file`, and
Jotai-related rules
- **Migrated custom rule tests** from ESLint `RuleTester` + Jest to
`oxlint/plugins-dev` `RuleTester` + Vitest
- **Removed all ESLint dependencies** from `package.json` files and
regenerated lockfiles
- **Updated Nx targets** (`lint`, `lint:diff-with-main`, `fmt`) in
`nx.json` and per-project `project.json` to use `oxlint` commands with
proper `dependsOn` for plugin builds
- **Updated CI workflows** (`.github/workflows/ci-*.yaml`) — no more
ESLint executor
- **Updated IDE setup**: replaced `dbaeumer.vscode-eslint` with
`oxc.oxc-vscode` extension, configured `source.fixAll.oxc` and
format-on-save with Prettier
- **Replaced all `eslint-disable` comments** with `oxlint-disable`
equivalents across the codebase
- **Updated docs** (`twenty-docs`) to reference OxLint instead of ESLint
- **Renamed** `twenty-eslint-rules` package to `twenty-oxlint-rules`

### Temporarily disabled rules (tracked in `OXLINT_MIGRATION_TODO.md`)

| Rule | Package | Violations | Auto-fixable |
|------|---------|-----------|-------------|
| `twenty/sort-css-properties-alphabetically` | twenty-front | 578 | Yes
|
| `typescript/consistent-type-imports` | twenty-server | 3814 | Yes |
| `twenty/max-consts-per-file` | twenty-server | 94 | No |

### Dropped plugins (no OxLint equivalent)

`eslint-plugin-project-structure`, `lingui/*`, `@stylistic/*`,
`import/order`, `prefer-arrow/prefer-arrow-functions`,
`eslint-plugin-mdx`, `@next/eslint-plugin-next`,
`eslint-plugin-storybook`, `eslint-plugin-react-refresh`. Partial
coverage for `jsx-a11y` and `unused-imports`.

### Additional fixes (pre-existing issues exposed by merge)

- Fixed `EmailThreadPreview.tsx` broken import from main rename
(`useOpenEmailThreadInSidePanel`)
- Restored truthiness guard in `getActivityTargetObjectRecords.ts`
- Fixed `AgentTurnResolver` return types to match entity (virtual
`fileMediaType`/`fileUrl` are resolved via `@ResolveField()`)

## Test plan

- [x] `npx nx lint twenty-front` passes
- [x] `npx nx lint twenty-server` passes
- [x] `npx nx lint twenty-docs` passes
- [x] Custom oxlint rules validated with Vitest: `npx nx test
twenty-oxlint-rules`
- [x] `npx nx typecheck twenty-front` passes
- [x] `npx nx typecheck twenty-server` passes
- [x] CI workflows trigger correctly with `dependsOn:
["twenty-oxlint-rules:build"]`
- [x] IDE linting works with `oxc.oxc-vscode` extension

packages/twenty-front/src/modules/object-record/object-options-dropdown/hooks/useObjectOptionsDropdown.ts

@@ -1,11 +1,12 @@
 import { useDropdownContextStateManagement } from '@/dropdown-context-state-management/hooks/useDropdownContextStateManagement';
 import { ObjectOptionsDropdownContext } from '@/object-record/object-options-dropdown/states/contexts/ObjectOptionsDropdownContext';
 import { useContext } from 'react';
+import { isDefined } from 'twenty-shared/utils';
 
 export const useObjectOptionsDropdown = () => {
   const context = useContext(ObjectOptionsDropdownContext);
 
-  if (!context) {
+  if (!isDefined(context)) {
     throw new Error('useObjectOptionsDropdown must be used within a context');
   }
 

packages/twenty-front/src/modules/object-record/object-options-dropdown/hooks/useObjectOptionsForBoard.ts

@@ -85,7 +85,7 @@ export const useObjectOptionsForBoard = ({
             recordIndexFieldDefinitionsByKey[fieldMetadataId];
 
           return {
-            ...(existingBoardField || availableColumnDefinition),
+            ...(existingBoardField ?? availableColumnDefinition),
             isVisible: false,
           };
         }),