refactor: move Dashboard to /apps, add Metrics sidebar entry, scope by app

- Route / redirects to /apps, Dashboard serves both /apps and /apps/:id
- When appId is present, exchanges/routes/agents/search are scoped to that app
- Remove Dashboards sidebar link, add Metrics link
- Sidebar section labels (Applications, Agents) are now clickable nav links
  with separate chevron for collapse toggle
- Update all breadcrumbs from Dashboard/href:'/' to Applications/href:'/apps'
- Remove AppDetail page (replaced by scoped Dashboard)

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

src/App.tsx

@@ -1,23 +1,23 @@
-import { Routes, Route } from 'react-router-dom'
+import { Routes, Route, Navigate } from 'react-router-dom'
 import { Dashboard } from './pages/Dashboard/Dashboard'
 import { Metrics } from './pages/Metrics/Metrics'
 import { RouteDetail } from './pages/RouteDetail/RouteDetail'
 import { ExchangeDetail } from './pages/ExchangeDetail/ExchangeDetail'
 import { AgentHealth } from './pages/AgentHealth/AgentHealth'
 import { Inventory } from './pages/Inventory/Inventory'
-import { AppDetail } from './pages/AppDetail/AppDetail'
 import { Admin } from './pages/Admin/Admin'
 import { ApiDocs } from './pages/ApiDocs/ApiDocs'
 
 export default function App() {
   return (
     <Routes>
-      <Route path="/" element={<Dashboard />} />
+      <Route path="/" element={<Navigate to="/apps" replace />} />
+      <Route path="/apps" element={<Dashboard />} />
+      <Route path="/apps/:id" element={<Dashboard />} />
       <Route path="/metrics" element={<Metrics />} />
       <Route path="/routes/:id" element={<RouteDetail />} />
       <Route path="/exchanges/:id" element={<ExchangeDetail />} />
       <Route path="/agents/*" element={<AgentHealth />} />
-      <Route path="/apps/:id" element={<AppDetail />} />
       <Route path="/admin" element={<Admin />} />
       <Route path="/api-docs" element={<ApiDocs />} />
       <Route path="/inventory" element={<Inventory />} />