feat: Phase 8 frontend - Customer identity core + standalone VK ID login button

core/identity (Customer/ExternalIdentity/ContactChannel models + VkIdGateway/
token/mock) and a standalone VkIdLoginComponent, per Sprint 0.1's "VK ID
first" decision and v3.1 §14. Against
docs/backend/PHASE-8-IDENTITY-MESSAGING-CONTRACT.md §1-2.

Deliberately not wired into TelegramLoginComponent's dialog - that's the
live, working QR-login surface for both customer and admin auth
(components/telegram-login/), and splicing a second provider into it
needs a real VK OAuth app to test against, not a mock bolt-on next to
nine other phases. The button is a standalone, ready-to-place component;
integrating it into checkout/login flows is follow-up work once VK
credentials exist.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/components/vk-id-login/vk-id-login.component.html

@@ -0,0 +1,4 @@
+<button type="button" class="vk-id-login" [disabled]="loading()" (click)="startLogin()">
+  <app-icon name="user" [size]="18" />
+  <span>Continue with VK ID</span>
+</button>

src/app/components/vk-id-login/vk-id-login.component.scss

@@ -0,0 +1,19 @@
+.vk-id-login {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 8px;
+  width: 100%;
+  padding: 10px 16px;
+  border: 1px solid var(--border-color);
+  border-radius: var(--radius-md);
+  background: var(--bg-primary);
+  color: var(--text-primary);
+  font-weight: var(--font-weight-bold, 700);
+  cursor: pointer;
+
+  &:disabled {
+    opacity: 0.6;
+    cursor: default;
+  }
+}

src/app/components/vk-id-login/vk-id-login.component.ts

@@ -0,0 +1,37 @@
+import { ChangeDetectionStrategy, Component, inject, signal } from '@angular/core';
+import { CommonModule } from '@angular/common';
+import { take } from 'rxjs/operators';
+import { VK_ID_GATEWAY } from '../../core/identity/services/vk-id-gateway.token';
+import { IconComponent } from '../../shared/ui/icon/icon.component';
+
+/**
+ * Standalone VK ID login button, per Sprint 0.1 ("do all after vk" - VK ID
+ * is the primary storefront social login going forward, per v3.1 §14).
+ * Deliberately not wired into TelegramLoginComponent's dialog yet - that
+ * component is the live, working customer/admin login surface, and
+ * splicing a second provider into it needs its own careful pass once a
+ * real VK OAuth app exists to test against, not a mock-backed bolt-on.
+ */
+@Component({
+  selector: 'app-vk-id-login',
+  standalone: true,
+  imports: [CommonModule, IconComponent],
+  templateUrl: './vk-id-login.component.html',
+  styleUrls: ['./vk-id-login.component.scss'],
+  changeDetection: ChangeDetectionStrategy.OnPush
+})
+export class VkIdLoginComponent {
+  private readonly gateway = inject(VK_ID_GATEWAY);
+
+  readonly loading = signal(false);
+
+  startLogin(): void {
+    this.loading.set(true);
+    this.gateway.getAuthorizeUrl().pipe(take(1)).subscribe(url => {
+      this.loading.set(false);
+      if (typeof window !== 'undefined') {
+        window.location.href = url;
+      }
+    });
+  }
+}