feat(client): add ContextMenu component, environment cards, detail page, and breadcrumbs

- add ContextMenu component with click-outside/Escape dismiss, align prop, and danger variant
- replace EnvironmentsPage table with responsive card grid
- add cog button to each card opening a context menu with view and delete actions
- add EnvironmentDetailPage at /environments/:id with meta grid, URLs card, and delete
- add Breadcrumbs to all pages; detail page uses two-item trail with delete button inline
- add Table stories for pagination and Timestamp column

client/src/ui/index.ts

@@ -27,5 +27,8 @@ export type { TimestampProps } from './Timestamp/Timestamp';
 export { Pagination } from './Pagination/Pagination';
 export type { PaginationProps } from './Pagination/Pagination';
 
+export { ContextMenu } from './ContextMenu/ContextMenu';
+export type { ContextMenuProps, ContextMenuItem } from './ContextMenu/ContextMenu';
+
 export { Table } from './Table/Table';
 export type { TableProps, TableColumn } from './Table/Table';