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>

packages/db/prisma/schema.prisma

@@ -24,6 +24,7 @@ model User {
   createdAt     DateTime       @default(now())
   updatedAt     DateTime       @updatedAt
   partEvents    PartEvent[]
+  hostEvents    HostEvent[]
   refreshTokens RefreshToken[]
   custodyParts  Part[]         @relation("Custody")
   repairs       Repair[]
@@ -198,11 +199,28 @@ model Host {
   parts     Part[]
   fms       Fm[]
   repairs   Repair[]
+  events    HostEvent[]
 
   @@index([state])
   @@index([stack])
 }
 
+model HostEvent {
+  id        String   @id @default(uuid())
+  hostId    String
+  host      Host     @relation(fields: [hostId], references: [id], onDelete: Cascade)
+  userId    String?
+  user      User?    @relation(fields: [userId], references: [id], onDelete: SetNull)
+  type      String
+  field     String?
+  oldValue  String?
+  newValue  String?
+  createdAt DateTime @default(now())
+
+  @@index([hostId, createdAt(sort: Desc)])
+  @@index([userId])
+}
+
 model Fm {
   id           String    @id @default(uuid())
   hostId       String