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/package.json

@@ -20,7 +20,8 @@
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
     "react-i18next": "^17.0.2",
-    "react-router-dom": "^7.14.0"
+    "react-router-dom": "^7.14.0",
+    "yaml": "^2.8.3"
   },
   "devDependencies": {
     "@eslint/js": "^9.39.4",