Fix app:dev CLI by removing deleted createOneApplication mutation (#18460)

## Summary
- The `createOneApplication` GraphQL mutation was removed from the
server during the application architecture refactor (#18432), but the
SDK CLI (`app:dev`, `app:build --sync`) still called it, causing
failures.
- Simplified the SDK to use `syncApplication` (which now internally
creates the `ApplicationEntity` via `ensureApplicationExists`) instead
of a separate create step.
- On first run (clean install), the orchestrator now runs an initial
sync before initializing the file uploader, so file uploads can proceed
(they require the `ApplicationEntity` to exist).

## Test plan
- [x] Typecheck passes for both `twenty-sdk` and `twenty-server`
- [x] `app:dev` tested locally with existing app (finds app, uploads,
syncs)
- [x] `app:dev` tested locally after `app:uninstall` (creates app via
sync, uploads, syncs)
- [x] SDK unit tests pass (23/26 files, 3 pre-existing failures
unrelated)

Made with [Cursor](https://cursor.com)

packages/create-twenty-app/src/utils/__tests__/test-template.spec.ts

@@ -47,7 +47,7 @@ describe('scaffoldIntegrationTest', () => {
       const content = await fs.readFile(testPath, 'utf8');
 
       expect(content).toContain(
-        "import { appBuild, appUninstall } from 'twenty-sdk/cli'",
+        "import { appGenerateClient, appUninstall } from 'twenty-sdk/cli'",
       );
       expect(content).toContain(
         "import { MetadataApiClient } from 'twenty-sdk/generated'",
@@ -57,7 +57,7 @@ describe('scaffoldIntegrationTest', () => {
       );
       expect(content).toContain('TWENTY_TEST_API_KEY');
       expect(content).toContain('assertServerIsReachable');
-      expect(content).toContain('appBuild');
+      expect(content).toContain('appGenerateClient');
       expect(content).toContain('appUninstall');
       expect(content).toContain('findManyApplications');
       expect(content).toContain('APPLICATION_UNIVERSAL_IDENTIFIER');