feat(export-import): add yaml export/import with id upsert for credentials, snippets, and scenarios

- all entities export a kind field (credential/snippet/scenario) for safe type checking on import
- import upserts by id: overwrites if id exists, creates with explicit id otherwise
- scenario export now includes id and step ids; import deletes old steps before recreating
- add GET /:id/export and POST /import endpoints to credential and snippet controllers
- add UuidBadge ui component: shortens uuid to first+last 4 hex chars, tooltip, clipboard copy with animated ClipboardCheck icon pop
- apply UuidBadge across all entity id display sites (detail pages, card footers, table columns)
- add export/import buttons to CredentialsPage, SnippetsPage, CredentialDetailPage, SnippetDetailPage

client/src/pages/session/SessionsPage.tsx

@@ -4,7 +4,7 @@ import { useTranslation } from 'react-i18next';
 import { Trash2 } from 'lucide-react';
 import { sessions } from '../../api';
 import type { Session } from '../../api';
-import { Badge, Breadcrumbs, Button, Table, type TableColumn, Timestamp } from '../../ui';
+import { Badge, Breadcrumbs, Button, Table, type TableColumn, Timestamp, UuidBadge } from '../../ui';
 import styles from '../Page.module.css';
 
 export function SessionsPage() {
@@ -26,14 +26,14 @@ export function SessionsPage() {
     load();
   }, [load]);
 
-  const handleDelete = async (id: number) => {
+  const handleDelete = async (id: string) => {
     await sessions.remove(id);
     setLoading(true);
     load();
   };
 
   const columns: TableColumn<Session>[] = [
-    { key: 'id', header: t('sessions.col_id'), render: (s) => s.id, width: 60 },
+    { key: 'id', header: t('sessions.col_id'), render: (s) => <UuidBadge id={s.id} />, width: 60 },
     { key: 'name', header: t('sessions.col_name'), render: (s) => s.sessionName },
     {
       key: 'status',