feat: Add Mantine theme, 12 atom components, and 25 molecule components with Storybook stories

- Mantine theme with component extensions (Badge, Card, Paper, Button, etc.)
- CSS custom properties for design tokens (--inspector-* vars)
- Dark/light mode support with auto detection
- 12 atoms: StatusIndicator, AnnotationBadge, CapabilityItem, LogEntry,
  ProgressDisplay, ContentViewer, ListChangedIndicator, CopyButton,
  ConnectionToggle, TransportBadge, InlineError, MessageBubble
- 25 molecules: ServerCard, AddServerMenu, SchemaForm, ToolListItem,
  ToolDetailPanel, ResultPanel, ResourceListItem, ResourcePreviewPanel,
  ResourceTemplateInput, PromptArgumentsForm, PromptMessagesDisplay,
  LogControls, TaskCard, HistoryEntry, ServerInfoContent, ServerSettingsForm,
  RootsTable, SamplingRequestPanel, ElicitationFormPanel, ElicitationUrlPanel,
  InlineSamplingRequest, InlineElicitationRequest, PendingClientRequests,
  ImportServerJsonPanel, ExperimentalFeaturesPanel
- Exclude storybook-static from version control
- Exclude .stories.tsx from app tsconfig (Storybook-only modules)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

clients/web/src/App.tsx

@@ -1,11 +1,39 @@
-import { Title, Text, Container, Stack } from '@mantine/core'
+import {
+  Title,
+  Text,
+  Container,
+  Stack,
+  useMantineColorScheme,
+  useComputedColorScheme,
+  ActionIcon,
+  Group,
+} from '@mantine/core'
 
 function App() {
+  const { setColorScheme } = useMantineColorScheme()
+  const computedColorScheme = useComputedColorScheme('light')
+
+  const toggleColorScheme = () => {
+    setColorScheme(computedColorScheme === 'dark' ? 'light' : 'dark')
+  }
+
   return (
     <Container size="sm" py="xl">
       <Stack align="center" gap="md">
-        <Title order={1}>MCP Inspector</Title>
-        <Text c="dimmed">Web client for the Model Context Protocol Inspector</Text>
+        <Group>
+          <Title order={1}>MCP Inspector</Title>
+          <ActionIcon
+            onClick={toggleColorScheme}
+            variant="default"
+            size="lg"
+            aria-label="Toggle color scheme"
+          >
+            {computedColorScheme === 'dark' ? '\u2600' : '\u263E'}
+          </ActionIcon>
+        </Group>
+        <Text c="var(--inspector-text-secondary)">
+          Web client for the Model Context Protocol Inspector
+        </Text>
       </Stack>
     </Container>
   )