feat: add comprehensive loading feedback (#18)

frontend/src/app/services/session.service.ts

@@ -7,22 +7,28 @@ interface UserResponse {
   email?: string;
 }
 
+export type SessionStatus = 'checking' | 'authenticated' | 'anonymous' | 'error';
+
 @Injectable({ providedIn: 'root' })
 export class SessionService {
   private readonly http = inject(HttpClient);
+  readonly status = signal<SessionStatus>('checking');
   readonly isLoggedIn = signal(false);
   readonly username = signal('');
   readonly email = signal('');
 
   refresh(): void {
+    this.status.set('checking');
     this.http.get<UserResponse>('/api/user').subscribe({
       next: (user) => {
         this.isLoggedIn.set(user.authenticated);
-        this.username.set(user.authenticated ? (user.username || 'User') : '');
-        this.email.set(user.authenticated ? (user.email || '') : '');
+        this.status.set(user.authenticated ? 'authenticated' : 'anonymous');
+        this.username.set(user.authenticated ? user.username || 'User' : '');
+        this.email.set(user.authenticated ? user.email || '' : '');
       },
       error: () => {
         this.isLoggedIn.set(false);
+        this.status.set('error');
         this.username.set('');
         this.email.set('');
       },