fix(twenty-front): fix tsconfig to properly typecheck all files with tsgo (#17380)

## Summary

This PR fixes the `tsconfig` setup in `twenty-front` so that `tsgo -p
tsconfig.json` properly type-checks all files.

### Root Cause

The previous setup used TypeScript project references with `files: []`
in the main `tsconfig.json`. When running `tsgo -p tsconfig.json`, this
checks nothing because `tsgo` requires the `-b` (build) flag for project
references, but the configs weren't set up for composite mode.

### Changes

**Simplified tsconfig architecture (4 files → 2):**
- `tsconfig.json` - All files (dev, tests, stories) for
typecheck/IDE/lint
- `tsconfig.build.json` - Production files only (excludes tests/stories)

**Removed redundant configs:**
- `tsconfig.dev.json`
- `tsconfig.spec.json` 
- `tsconfig.storybook.json`

**Updated references:**
- `jest.config.mjs` → uses `tsconfig.json`
- `eslint.config.mjs` → uses `tsconfig.json`
- `vite.config.ts` → uses `tsconfig.json` for dev

**Type fixes (pre-existing errors revealed by proper typechecking):**
- Made `applicationId` optional in `FieldMetadataItem` and
`ObjectMetadataItem`
- Added missing `navigationMenuItem` translation
- Added `objectLabelSingular` to Search GraphQL query
- Fixed `sortMorphItems.test.ts` mock data

## Test plan

- [ ] Run `npx nx typecheck twenty-front` - should pass
- [ ] Run `npx nx lint twenty-front` - should work
- [ ] Run `npx nx test twenty-front` - should work
- [ ] Run `npx nx build twenty-front` - should work
- [ ] Verify IDE type checking works correctly

packages/twenty-shared/src/utils/validation/isValidLocale.ts

@@ -1,5 +1,4 @@
-import { APP_LOCALES } from '@/translations';
+import { APP_LOCALES, type AppLocale } from '@/translations/constants/AppLocales';
 
-export const isValidLocale = (
-  value: string | null,
-): value is keyof typeof APP_LOCALES => value !== null && value in APP_LOCALES;
+export const isValidLocale = (value: string | null): value is AppLocale =>
+  value !== null && value in APP_LOCALES;