feat: harness VM stack (runner, measure-db, blackbox, Alloy, k6) and the 12 scenarios

Experiment design 5 and 7 for the harness VM (10.20.0.11): vm/harness/apply.sh pulls the secrets from Secret Manager,
compose runs runner:de076a7, measure-db, blackbox, Alloy (probe_success -> Mimir) and k6 under the campaign profile.
Scenario files C-K1..X-M2 are loaded by the runner. Harness ClusterRole gains replicasets get/list for rollout undo.

vm/harness/blackbox.yaml

@@ -0,0 +1,14 @@
+# blackbox exporter modules (design 4.1): http_2xx for the ALB path, tcp_connect for db-primary:5432
+modules:
+  http_2xx:
+    prober: http
+    timeout: 10s
+    http:
+      preferred_ip_protocol: ip4
+      valid_status_codes: [200]
+      method: GET
+  tcp_connect:
+    prober: tcp
+    timeout: 5s
+    tcp:
+      preferred_ip_protocol: ip4