feat(ui): animated boot splash and loading screen

Show a Lottie-animated splash while the app bundle boots and dismiss it
once WebAppComponent initialises, plus a reusable mifosx-loading-screen
component with loading and error animations. lottie.min.js is served
from the lottie-web package instead of being vendored into src/assets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/app.module.ts

@@ -96,6 +96,7 @@ import { TokenInterceptor as ZitadelTokenInterceptor } from './zitadel/token.int
 import { AuthService } from './zitadel/auth.service';
 import { environment } from '../environments/environment';
 import { CallbackComponent } from './zitadel/callback/callback.component';
+import { LoadingScreenComponent } from './shared/loading-screen/loading-screen.component';
 import { OAuthModule } from 'angular-oauth2-oidc';
 
 export class CustomMissingTranslationHandler implements MissingTranslationHandler {
@@ -195,6 +196,7 @@ export function HttpLoaderFactory(http: HttpClient) {
     AppRoutingModule,
     NotFoundComponent,
     CallbackComponent,
+    LoadingScreenComponent,
     OAuthModule.forRoot()
   ],
   providers: [