feat: add comprehensive loading feedback (#18)

frontend/src/app/app.ts

@@ -1,4 +1,6 @@
 import { Component, computed, inject, OnInit } from '@angular/core';
+import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
+import { MatButtonModule } from '@angular/material/button';
 import { RouterOutlet } from '@angular/router';
 import { BrandMark } from './components/brand-mark';
 import { SignInPage } from './components/sign-in-page/sign-in-page';
@@ -12,6 +14,8 @@ import { SessionService } from './services/session.service';
     SignInPage,
     WorkspaceNavigation,
     RouterOutlet,
+    MatProgressSpinnerModule,
+    MatButtonModule,
   ],
   templateUrl: './app.html',
   styleUrl: './app.css',
@@ -31,5 +35,4 @@ export class App implements OnInit {
   logout() {
     window.location.href = '/logout';
   }
-
 }