feat: initial prototype works

I can log in and create a book! Woo!

apps/frontend/src/app/interceptors/auth.interceptor.ts

@@ -0,0 +1,39 @@
+/**
+ * @copyright 2026 NHCarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+import { Injectable } from '@angular/core';
+import {
+  HttpRequest,
+  HttpHandler,
+  HttpEvent,
+  HttpInterceptor,
+  HttpErrorResponse
+} from '@angular/common/http';
+import { Observable, catchError, throwError } from 'rxjs';
+import { Router } from '@angular/router';
+
+@Injectable()
+export class AuthInterceptor implements HttpInterceptor {
+  constructor(private router: Router) {}
+
+  intercept(request: HttpRequest<unknown>, next: HttpHandler): Observable<HttpEvent<unknown>> {
+    // Clone the request to add withCredentials
+    // This ensures cookies are sent with every request
+    const authReq = request.clone({
+      withCredentials: true
+    });
+
+    return next.handle(authReq).pipe(
+      catchError((error: HttpErrorResponse) => {
+        if (error.status === 401) {
+          // Unauthorized - redirect to home
+          this.router.navigate(['/']);
+        }
+        return throwError(() => error);
+      })
+    );
+  }
+}