observability: fix alloy ui component, busybox healthchecks for loki/alloy

- alloy 1.x renamed the server component to ui; the old block failed the
  initial load and the container crash-looped
- grafana/loki is distroless and grafana/alloy lacks wget, so their
  healthchecks could never run; local images add a static busybox from
  alpine for that one command
- deploy.sh builds all three local images if missing
- tests: 3 new seams

shared/alloy/config.alloy

@@ -6,9 +6,10 @@ logging {
 }
 
 // Local listener so the container healthcheck can probe us.
-server {
-  http_listen_addr = "0.0.0.0:12345"
-  grpc_listen_addr = "0.0.0.0:12346"
+// Alloy >= 1.0 renamed the server component to ui.
+ui {
+  host = "0.0.0.0"
+  port = 12345
 }
 
 // Ship logs to Loki (container name on the podman network).