feat(deploy): blackbox copier, alloy engine-validation gate, planner wiring

copy_alloy_config now validates the rendered config with the very
alloy image that will run it, before installing: a misplaced attribute
crash-loops the unit behind a green deploy, and no textual seam can
see it. copy_blackbox_config ships the prober config; the planner maps
the new unit and shared/blackbox/** to the blackbox-exporter service,
ordered before prometheus.

scripts/deploy-plan.py

@@ -34,7 +34,6 @@ SERVICE_ORDER = (
     "hermes",
     "hermes-dashboard",
     "hermes-webui",
-    "prometheus",
     "grafana",
     "loki",
     "alloy",
@@ -42,6 +41,9 @@ SERVICE_ORDER = (
     "cadvisor",
     "gpu-exporter",
     "alertmanager",
+    # The prober must answer before prometheus re-runs the services job.
+    "blackbox-exporter",
+    "prometheus",
     "authentik-postgres",
     "authentik-server",
     "authentik-worker",
@@ -97,6 +99,7 @@ DANKCLAW_SERVICES = {
     "cadvisor",
     "gpu-exporter",
     "alertmanager",
+    "blackbox-exporter",
     "authentik-postgres",
     "authentik-server",
     "authentik-worker",
@@ -277,6 +280,8 @@ def services_for_path(path: str, target: str) -> set[str]:
             # Provisioned datasources and dashboards: git is the source of
             # truth, so a change here must restart the service that reads them.
             _add(services, "grafana")
+        elif group == "blackbox":
+            _add(services, "blackbox-exporter")
         elif group == "homepage":
             # Homepage is a Dankclaw-owned deployment. Shared homepage files
             # are intentionally not copied during a Dankserver-only run.
@@ -380,7 +385,7 @@ def services_for_path(path: str, target: str) -> set[str]:
             # consumer (prometheus before grafana, loki before alloy).
             if len(parts) >= 4 and parts[2] == "quadlet":
                 name = parts[3].removesuffix(".container")
-                if name in {"prometheus", "grafana", "loki", "alloy", "node-exporter", "cadvisor", "alertmanager"}:
+                if name in {"prometheus", "grafana", "loki", "alloy", "node-exporter", "cadvisor", "alertmanager", "blackbox-exporter"}:
                     _add(services, name)
             return services
         if len(parts) >= 2 and parts[1] == "gitea":