feat(ui): add CodeBlock and CodeEditor components with Monaco and hljs

- add CodeBlock for read-only syntax-highlighted display (hljs, js/json)
- add CodeEditor wrapping Monaco editor with theme sync, focus state, and error state
- replace code textareas in snippet, credential, and step pages with CodeEditor
- replace code <pre> blocks in snippet and credential detail pages with CodeBlock
- make form cards full-width on pages with code editors
- add resize:vertical support to CodeEditor wrapper with automaticLayout

client/src/ui/index.ts

@@ -36,6 +36,12 @@ export type { PaginationProps } from './Pagination/Pagination';
 export { Search } from './Search/Search';
 export type { SearchProps } from './Search/Search';
 
+export { CodeBlock } from './CodeBlock/CodeBlock';
+export type { CodeBlockProps } from './CodeBlock/CodeBlock';
+
+export { CodeEditor } from './CodeEditor/CodeEditor';
+export type { CodeEditorProps } from './CodeEditor/CodeEditor';
+
 export { ContextMenu } from './ContextMenu/ContextMenu';
 export type { ContextMenuProps, ContextMenuItem } from './ContextMenu/ContextMenu';