feat(ui/alerts): mount NotificationBell in TopBar

Renders the `<NotificationBell />` as the first child of `<TopBar>` (before
`<SearchTrigger>`). The bell links to `/alerts/inbox` and shows the unread
alert count for the currently selected environment.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/src/components/LayoutShell.tsx

@@ -23,6 +23,7 @@ import type { SearchResult, SidebarTreeNode, DropdownItem, ButtonGroupItem, Exch
 import sidebarLogo from '@cameleer/design-system/assets/cameleer-logo.svg';
 import { Box, Settings, FileText, ChevronRight, Square, Pause, Star, X, User, Plus, EyeOff, Bell } from 'lucide-react';
 import { AboutMeDialog } from './AboutMeDialog';
+import { NotificationBell } from './NotificationBell';
 import css from './LayoutShell.module.css';
 import { useQueryClient } from '@tanstack/react-query';
 import { useCatalog } from '../api/queries/catalog';
@@ -899,6 +900,7 @@ function LayoutContent() {
         onLogout={handleLogout}
         onNavigate={navigate}
       >
+        <NotificationBell />
         <SearchTrigger onClick={() => setPaletteOpen(true)} />
         <ButtonGroup
           items={STATUS_ITEMS}