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/credential/CredentialDetailPage.tsx

@@ -6,7 +6,15 @@ import { CodeBlock } from '../../ui';
 import { stringify as yamlStringify } from 'yaml';
 import { credentials } from '../../api';
 import type { Credential } from '../../api';
-import { Breadcrumbs, Button, Card, DescriptionList, Notification, Timestamp, UuidBadge } from '../../ui';
+import {
+  Breadcrumbs,
+  Button,
+  Card,
+  DescriptionList,
+  Notification,
+  Timestamp,
+  UuidBadge,
+} from '../../ui';
 import styles from '../Page.module.css';
 
 export function CredentialDetailPage() {
@@ -95,11 +103,7 @@ export function CredentialDetailPage() {
                 { term: t('credentials.field_id'), detail: <UuidBadge id={credential.id} /> },
                 {
                   term: t('credentials.field_last_used'),
-                  detail: credential.lastUsedAt ? (
-                    <Timestamp value={credential.lastUsedAt} />
-                  ) : (
-                    '—'
-                  ),
+                  detail: credential.lastUsedAt ? <Timestamp value={credential.lastUsedAt} /> : '—',
                 },
                 {
                   term: t('credentials.field_created'),