docs: use the @Service decorator in the first-app and signals tutorials

Update the services in the first-app and signals tutorials to use the
`@Service()` decorator instead of `@Injectable({providedIn: 'root'})`.
This affects `HousingService` (first-app steps 10-14) and `CartStore`
(signals step 7).

adev/src/content/tutorials/first-app/steps/10-routing/src/app/housing.service.ts

@@ -1,8 +1,6 @@
-import {Injectable} from '@angular/core';
+import {Service} from '@angular/core';
 import {HousingLocationInfo} from './housinglocation';
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class HousingService {
   readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';
 

adev/src/content/tutorials/first-app/steps/11-details-page/src/app/housing.service.ts

@@ -1,9 +1,7 @@
-import {Injectable} from '@angular/core';
+import {Service} from '@angular/core';
 import {HousingLocationInfo} from './housinglocation';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class HousingService {
   readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';
 

adev/src/content/tutorials/first-app/steps/12-forms/src/app/housing.service.ts

@@ -1,9 +1,7 @@
-import {Injectable} from '@angular/core';
+import {Service} from '@angular/core';
 import {HousingLocationInfo} from './housinglocation';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class HousingService {
   readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';
 

adev/src/content/tutorials/first-app/steps/13-search/src/app/housing.service.ts

@@ -1,9 +1,7 @@
-import {Injectable} from '@angular/core';
+import {Service} from '@angular/core';
 import {HousingLocationInfo} from './housinglocation';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class HousingService {
   readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';
 

adev/src/content/tutorials/first-app/steps/14-http/src-final/app/housing.service.ts

@@ -1,9 +1,7 @@
-import {Injectable} from '@angular/core';
+import {Service} from '@angular/core';
 import {HousingLocationInfo} from './housinglocation';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class HousingService {
   url = 'http://localhost:3000/locations';
 

adev/src/content/tutorials/first-app/steps/14-http/src/app/housing.service.ts

@@ -1,9 +1,7 @@
-import {Injectable} from '@angular/core';
+import {Service} from '@angular/core';
 import {HousingLocationInfo} from './housinglocation';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class HousingService {
   readonly baseUrl = 'https://angular.dev/assets/images/tutorials/common';
 

adev/src/content/tutorials/signals/steps/7-using-signals-with-services/README.md

@@ -13,7 +13,7 @@ Add readonly and computed signals to make the cart state reactive in `cart-store
 
 ```ts
 // Add the computed import
-import {Injectable, signal, computed} from '@angular/core';
+import {Service, signal, computed} from '@angular/core';
 
 // Then add these signals to the class:
 

adev/src/content/tutorials/signals/steps/7-using-signals-with-services/answer/src/app/cart-store.ts

@@ -1,9 +1,7 @@
-import {Injectable, signal, computed} from '@angular/core';
+import {Service, signal, computed} from '@angular/core';
 import {CartItem} from './cart-types';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class CartStore {
   private items = signal<CartItem[]>([]);
 

adev/src/content/tutorials/signals/steps/7-using-signals-with-services/src/app/cart-store.ts

@@ -1,10 +1,8 @@
 // TODO: Import computed from @angular/core
-import {Injectable, signal} from '@angular/core';
+import {Service, signal} from '@angular/core';
 import {CartItem} from './cart-types';
 
-@Injectable({
-  providedIn: 'root',
-})
+@Service()
 export class CartStore {
   private items = signal<CartItem[]>([]);