fix(gateway/auth): Implement proper auth/init flow with automatic background userId generation

- Fix getUserId() to use placeholder that triggers auth/init if the auth/init endpoint is down for whatever reason
- Add silent auth/init attempt in AI services
- Improve hosted mode error handling
- Remove fake userId/email generation from init.js

tests/unit/scripts/modules/telemetry-enhancements.test.js

@@ -25,6 +25,7 @@ jest.unstable_mockModule(
     getAzureBaseURL: jest.fn(),
     getVertexProjectId: jest.fn(),
     getVertexLocation: jest.fn(),
+    writeConfig: jest.fn(() => true),
     MODEL_MAP: {
       openai: [
         {