feat: host detail page + FM host context

Add /hosts/:id detail page with unified timeline (HostEvents + FMs + Repairs
+ part arrivals/departures) and a deployed-parts table. Hosts list rows now
link to the page. FM list + detail surface inline State/Stack badges next
to the asset ID, with the asset ID linking to the host page.

HostEvent audit model added; create/update in the hosts service now diff
and log state, stack, and field changes the same way parts.ts does.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/App.tsx

@@ -18,6 +18,7 @@ import FmDetail from './pages/FmDetail.js';
 import Repairs from './pages/Repairs.js';
 import MyCustody from './pages/MyCustody.js';
 import Hosts from './pages/Hosts.js';
+import HostDetail from './pages/HostDetail.js';
 import Users from './pages/admin/Users.js';
 import Webhooks from './pages/admin/Webhooks.js';
 
@@ -64,6 +65,7 @@ export default function App() {
                     <Route path="/repairs" element={<Repairs />} />
                     <Route path="/custody" element={<MyCustody />} />
                     <Route path="/hosts" element={<Hosts />} />
+                    <Route path="/hosts/:id" element={<HostDetail />} />
                     <Route
                       path="/admin/users"
                       element={