feat(remote): route service checks through their hosting compute entity

A service check used to bake its hosting LXC's lan_ip and SSH it directly as
root, which failed because the scheduler key is authorized on the Proxmox hosts
but not inside every guest — leaving all 8 service process checks 'down' even
after the guest routing and scripts were fixed.

ResolveExecTargetForCheck now, for a non-guest target, walks the
provides/runs-on/hosts edges to the compute entity that runs it and routes
through that: pct/qm exec if the host is a guest, direct SSH with the host's
correct user (workstation `user` attr) if it's a machine. The guest-resolution
path is shared via resolveGuest, and the scheduler no longer needs an
isMachine special case — one resolver handles guest, machine, and service.

internal/remote/remote_test.go

@@ -170,3 +170,34 @@ func TestResolveExecTargetForCheckHostIsDirect(t *testing.T) {
 		t.Errorf("host wrap must be identity, got %q", cmd)
 	}
 }
+
+func TestResolveExecTargetForCheckServiceRoutesViaHostingGuest(t *testing.T) {
+	// A service has no address of its own; it must route through its hosting
+	// LXC via the provides edge, host-hopping through the LXC's proxmox host.
+	pool := newRemotePool(t)
+	ctx := context.Background()
+	hostID := uuid.New()
+	guestID := uuid.New()
+	svcID := uuid.New()
+	mustExec(t, pool, ctx, `INSERT INTO entities (id, slug, type, name, state, attributes, version, created_at, updated_at)
+		VALUES ($1,'host:hubris','proxmox-host','hubris','active','{"lan_ip":"192.168.8.77"}'::jsonb,1,now(),now())`, hostID)
+	mustExec(t, pool, ctx, `INSERT INTO entities (id, slug, type, name, state, attributes, version, created_at, updated_at)
+		VALUES ($1,'lxc:gitea','lxc','gitea','active','{"pve_id":"104","lan_ip":"192.168.8.121"}'::jsonb,1,now(),now())`, guestID)
+	mustExec(t, pool, ctx, `INSERT INTO entities (id, slug, type, name, state, attributes, version, created_at, updated_at)
+		VALUES ($1,'service:gitea','service','gitea','active','{}'::jsonb,1,now(),now())`, svcID)
+	// provides: lxc -> service; hosts: proxmox-host -> lxc
+	mustExec(t, pool, ctx, `INSERT INTO relationships (source_id, target_id, type, valid_from, created_at) VALUES ($1,$2,'provides',now(),now())`, guestID, svcID)
+	mustExec(t, pool, ctx, `INSERT INTO relationships (source_id, target_id, type, valid_from, created_at) VALUES ($1,$2,'hosts',now(),now())`, hostID, guestID)
+
+	et, err := ResolveExecTargetForCheck(ctx, pool, svcID, "service", DefaultUser)
+	if err != nil {
+		t.Fatalf("ResolveExecTargetForCheck for service: %v", err)
+	}
+	// Reaches the proxmox host (host-hop), wrapped as pct exec into the guest.
+	if et.Host != "192.168.8.77" {
+		t.Errorf("Host = %q, want proxmox host 192.168.8.77 (via provides->hosts)", et.Host)
+	}
+	if out := et.Wrap("p"); !strings.Contains(out, "pct exec 104") {
+		t.Errorf("service check must wrap as pct exec 104, got %q", out)
+	}
+}