feat: update hotel service to use observables

src/app/app.component.html

@@ -1,11 +1,7 @@
 <h1>{{'hello' | uppercase | text}}</h1>
 <app-search [(input)]="search"></app-search>
-@for (hotel of hotels; track hotel.hotelId) {
-  @let should_show = search === "" || hotel.hotelName.includes(search);
-  @if (should_show) {
+@for (let hotel of foundHotels | async) {
+  @if (search === "") {
     <app-hotel-item [hotel]="hotel"></app-hotel-item>
   }
 }
-@if (!has_hotels()) {
-  <p>No hotels found</p>
-}