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

server/src/snippet/snippet.entity.ts

@@ -8,8 +8,8 @@ import {
 
 @Entity("snippets")
 export class SnippetEntity {
-  @PrimaryGeneratedColumn()
-  id: number;
+  @PrimaryGeneratedColumn("uuid")
+  id: string;
 
   /** Unique identifier used to call the snippet: helpers.runSnippet('mySnippet', ...) */
   @Column({ unique: true })