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/migrations/20260417175214_add_host_event/migration.sql

@@ -0,0 +1,19 @@
+-- CreateTable
+CREATE TABLE "HostEvent" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "hostId" TEXT NOT NULL,
+    "userId" TEXT,
+    "type" TEXT NOT NULL,
+    "field" TEXT,
+    "oldValue" TEXT,
+    "newValue" TEXT,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "HostEvent_hostId_fkey" FOREIGN KEY ("hostId") REFERENCES "Host" ("id") ON DELETE CASCADE ON UPDATE CASCADE,
+    CONSTRAINT "HostEvent_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User" ("id") ON DELETE SET NULL ON UPDATE CASCADE
+);
+
+-- CreateIndex
+CREATE INDEX "HostEvent_hostId_createdAt_idx" ON "HostEvent"("hostId", "createdAt" DESC);
+
+-- CreateIndex
+CREATE INDEX "HostEvent_userId_idx" ON "HostEvent"("userId");