chore(images): pin service image updates

Replace floating service images with reviewable tags or digests.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

uptime-kuma/compose.yaml

@@ -1,6 +1,6 @@
 services:
   uptime-kuma:
-    image: louislam/uptime-kuma:2
+    image: louislam/uptime-kuma:2.5.4
     container_name: uptime-kuma
     restart: unless-stopped
     volumes:

uptime-kuma/k8s/uptime-kuma.yaml

@@ -27,7 +27,7 @@ spec:
     spec:
       containers:
         - name: uptime-kuma
-          image: louislam/uptime-kuma:2
+          image: louislam/uptime-kuma:2.5.4
           resources:
             limits:
               memory: "3Gi"