Add auth-client library for Elixir auth service integration

- Complete Angular client library for authentication and authorization
- JWT token management with automatic refresh and storage
- OAuth integration with social providers (Google, GitHub, etc.)
- Two-factor authentication support (TOTP and backup codes)
- Route guards for authentication and scope-based authorization
- HTTP interceptor for automatic token injection and refresh
- Comprehensive TypeScript interfaces for all API models
- User management features (profile updates, password changes)
- Cross-tab synchronization and token validation
- Complete usage guide with practical examples

🤖 Generated with [Claude Code](https://claude.ai/code)

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

projects/auth-client/src/lib/guards/auth.guard.ts

@@ -0,0 +1,67 @@
+import { Injectable } from '@angular/core';
+import { CanActivate, CanActivateChild, ActivatedRouteSnapshot, RouterStateSnapshot, Router } from '@angular/router';
+import { Observable, of } from 'rxjs';
+import { map, take, tap } from 'rxjs/operators';
+import { AuthService } from '../services/auth.service';
+
+@Injectable({
+  providedIn: 'root'
+})
+export class AuthGuard implements CanActivate, CanActivateChild {
+  constructor(
+    private authService: AuthService,
+    private router: Router
+  ) {}
+
+  canActivate(
+    route: ActivatedRouteSnapshot,
+    state: RouterStateSnapshot
+  ): Observable<boolean> {
+    return this.checkAuth(route, state.url);
+  }
+
+  canActivateChild(
+    childRoute: ActivatedRouteSnapshot,
+    state: RouterStateSnapshot
+  ): Observable<boolean> {
+    return this.canActivate(childRoute, state);
+  }
+
+  private checkAuth(route: ActivatedRouteSnapshot, redirectUrl: string): Observable<boolean> {
+    return this.authService.isAuthenticated$.pipe(
+      take(1),
+      map(isAuthenticated => {
+        if (isAuthenticated) {
+          // Check for required scopes if specified
+          const requiredScopes = route.data?.['requiredScopes'] as string[];
+          if (requiredScopes && requiredScopes.length > 0) {
+            const hasScopes = route.data?.['requireAllScopes'] 
+              ? this.authService.hasAllScopes(requiredScopes)
+              : this.authService.hasAnyScope(requiredScopes);
+            
+            if (!hasScopes) {
+              this.handleUnauthorized(route.data?.['unauthorizedRedirect']);
+              return false;
+            }
+          }
+          return true;
+        } else {
+          this.handleUnauthenticated(redirectUrl, route.data?.['loginRedirect']);
+          return false;
+        }
+      })
+    );
+  }
+
+  private handleUnauthenticated(redirectUrl: string, customLoginPath?: string): void {
+    const loginPath = customLoginPath || '/login';
+    this.router.navigate([loginPath], {
+      queryParams: { returnUrl: redirectUrl }
+    });
+  }
+
+  private handleUnauthorized(customUnauthorizedPath?: string): void {
+    const unauthorizedPath = customUnauthorizedPath || '/unauthorized';
+    this.router.navigate([unauthorizedPath]);
+  }
+}