refactor(scenario): remove step type and simplify scheduler to exec-only

- remove StepType, type column, and type field from step entity and DTOs
- remove executeLoginStep, executeSignStep, executeExecStep from scheduler
- inline exec logic directly in executeStepRun; all steps run execCode
- remove AuthService, EnvironmentService, runEnvironments from scheduler
- remove type selector from CreateStepPage and EditStepPage
- remove type badge column from ScenarioDetailPage
- fix useEffect dependency arrays in RunDetailPage (FINAL, id, runId, polling)
- fix duplicate /snippets proxy key in vite.config.ts
- remove unused escapeHtml export from hljs.ts

client/src/pages/environment/EnvironmentsPage.tsx

@@ -4,7 +4,15 @@ import { useTranslation } from 'react-i18next';
 import { Settings, ExternalLink, Pencil, Trash2, Plus } from 'lucide-react';
 import { environments } from '../../api';
 import type { Environment } from '../../api';
-import { Breadcrumbs, Button, Card, ContextMenu, DescriptionList, Timestamp, UuidBadge } from '../../ui';
+import {
+  Breadcrumbs,
+  Button,
+  Card,
+  ContextMenu,
+  DescriptionList,
+  Timestamp,
+  UuidBadge,
+} from '../../ui';
 import styles from '../Page.module.css';
 
 function EnvironmentCard({ env, onDelete }: { env: Environment; onDelete: (id: string) => void }) {