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/snippet/SnippetsPage.tsx

@@ -8,13 +8,7 @@ import type { Snippet } from '../../api';
 import { Breadcrumbs, Button, Card, ContextMenu, Timestamp, UuidBadge } from '../../ui';
 import styles from '../Page.module.css';
 
-function SnippetCard({
-  snippet,
-  onDelete,
-}: {
-  snippet: Snippet;
-  onDelete: (id: string) => void;
-}) {
+function SnippetCard({ snippet, onDelete }: { snippet: Snippet; onDelete: (id: string) => void }) {
   const { t } = useTranslation();
   const navigate = useNavigate();
 
@@ -62,9 +56,7 @@ function SnippetCard({
       footer={footer}
       onClick={() => navigate(`/snippets/${snippet.id}`)}
     >
-      {snippet.description && (
-        <p className={styles.muted}>{snippet.description}</p>
-      )}
+      {snippet.description && <p className={styles.muted}>{snippet.description}</p>}
     </Card>
   );
 }
@@ -148,9 +140,7 @@ export function SnippetsPage() {
           {items.map((s) => (
             <SnippetCard key={s.id} snippet={s} onDelete={handleDelete} />
           ))}
-          {items.length === 0 && (
-            <p className={styles.muted}>{t('snippets.empty')}</p>
-          )}
+          {items.length === 0 && <p className={styles.muted}>{t('snippets.empty')}</p>}
           <AddSnippetCard />
         </div>
       )}