hub: shared host_detail_body sub-template + customer Host tab (v0.47.0 part 3)

- host_detail_body.html: {{define}}'d body sections extracted from
  host_detail.html; the standalone page is now chrome + the sub-template
- hosts.go: hostDetailData(host, r) view-model builder extracted from
  handleHostDetail (reused by both surfaces)
- store: ListHostsByCustomer (host_id order; the Host tab is a list by
  design - N hosts for a future HA cluster)
- customer Host tab renders one host_detail_body per host + cross-link;
  empty state when no host is enrolled
- tests: TestTemplates_CustomerHostTab(+_Empty), TestListHostsByCustomer

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vvz1NCu22p8dGkRCpeX9re

hub/internal/store/host_test.go

@@ -86,6 +86,33 @@ func TestGetHostByCustomer(t *testing.T) {
 	}
 }
 
+// v0.47.0 Host tab: ListHostsByCustomer returns ONLY the customer's hosts, ordered by
+// host_id, and leaves other customers' hosts out (isolation).
+func TestListHostsByCustomer(t *testing.T) {
+	s := newTestStore(t)
+	for _, h := range []Host{
+		{HostID: "c1-bbb", CustomerID: "c1", APIKey: "k2"},
+		{HostID: "c1-aaa", CustomerID: "c1", APIKey: "k1"},
+		{HostID: "c2-zzz", CustomerID: "c2", APIKey: "k3"},
+	} {
+		h := h
+		if err := s.UpsertHost(&h); err != nil {
+			t.Fatal(err)
+		}
+	}
+	got, err := s.ListHostsByCustomer("c1")
+	if err != nil {
+		t.Fatalf("ListHostsByCustomer: %v", err)
+	}
+	if len(got) != 2 || got[0].HostID != "c1-aaa" || got[1].HostID != "c1-bbb" {
+		t.Fatalf("c1 hosts = %+v (want [c1-aaa c1-bbb])", got)
+	}
+	none, err := s.ListHostsByCustomer("c3")
+	if err != nil || len(none) != 0 {
+		t.Fatalf("c3 hosts = %+v / %v (want empty)", none, err)
+	}
+}
+
 func TestSaveHostReport_BumpsRealityPreservesIntent(t *testing.T) {
 	s := newTestStore(t)
 	if err := s.UpsertHost(&Host{HostID: "h1", CustomerID: "c1", APIKey: "k1"}); err != nil {