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/.storybook/stories/ContextMenu.stories.tsx

@@ -0,0 +1,52 @@
+import type { Meta, StoryObj } from '@storybook/react-vite';
+import { Settings, Trash2, ExternalLink } from 'lucide-react';
+import { Button } from '../../src/ui/Button/Button';
+import { ContextMenu } from '../../src/ui/ContextMenu/ContextMenu';
+
+const meta: Meta<typeof ContextMenu> = {
+  title: 'UI/ContextMenu',
+  component: ContextMenu,
+  parameters: { layout: 'centered' },
+  tags: ['autodocs'],
+};
+export default meta;
+type Story = StoryObj<typeof ContextMenu>;
+
+const trigger = (
+  <Button variant="ghost" size="sm">
+    <Settings size={16} />
+  </Button>
+);
+
+export const Default: Story = {
+  args: {
+    trigger,
+    items: [
+      { label: 'View details', icon: <ExternalLink size={14} />, onClick: () => {} },
+      { label: 'Delete', icon: <Trash2 size={14} />, variant: 'danger', onClick: () => {} },
+    ],
+  },
+};
+
+export const AlignLeft: Story = {
+  args: {
+    trigger,
+    align: 'left',
+    items: [
+      { label: 'View details', icon: <ExternalLink size={14} />, onClick: () => {} },
+      { label: 'Delete', icon: <Trash2 size={14} />, variant: 'danger', onClick: () => {} },
+    ],
+  },
+};
+
+export const ManyItems: Story = {
+  args: {
+    trigger,
+    items: [
+      { label: 'View details', icon: <ExternalLink size={14} />, onClick: () => {} },
+      { label: 'Edit', icon: <Settings size={14} />, onClick: () => {} },
+      { label: 'Duplicate', onClick: () => {} },
+      { label: 'Delete', icon: <Trash2 size={14} />, variant: 'danger', onClick: () => {} },
+    ],
+  },
+};