Remove unused VK OAuth env vars (VK_CLIENT_ID/SECRET/SCOPES)

VK connection now uses manual community token entry, so OAuth credentials
are no longer needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -5,9 +5,6 @@ BASE_URL=http://localhost:8000
 EVOTOR_APP_ID=your-evotor-app-id
 EVOTOR_WEBHOOK_SECRET=your-webhook-secret
 
-VK_CLIENT_ID=your-vk-client-id
-VK_CLIENT_SECRET=your-vk-client-secret
-
 DB_ROOT_PASSWORD=rootpass
 DB_NAME=evosync
 DB_USER=evosync