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/pages/Inventory/Inventory.tsx

@@ -15,7 +15,7 @@ export function Inventory() {
     <div className={styles.page}>
       <header className={styles.header}>
         <h1 className={styles.headerTitle}>Component Inventory</h1>
-        <Link to="/" className={styles.backLink}>← Back to app</Link>
+        <Link to="/apps" className={styles.backLink}>← Back to app</Link>
       </header>
 
       <div className={styles.body}>