Revert "LIVE-TEST (controller v0.238.0 slice 4 Scenario F), REVERTED IN THE SAME SESSION: uptime-kuma 2.4.0 -> alpine:3.20"

This reverts commit 6ce3f65, reverted EARLY — as soon as the update under test had advanced its pin,
which is the last moment the catalog value mattered to Scenario F. Flagged by the commit security
review (supply-chain: a catalog push is a deploy, and any fresh uptime-kuma install in that window
would have received an image that exits at once). Measured exposure: demo-hp's throwaway was the only
uptime-kuma install on either demo box. catalog_since is back to its original value.

Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

templates/uptime-kuma/.felhom.yml

@@ -10,7 +10,7 @@ subdomain: "status"
 slug: "uptime-kuma"
 # catalog_since: the date THIS repo last changed this app's pinned images. Any commit that
 # changes an image: line must set this to the same day (see CLAUDE.md).
-catalog_since: "2026-09-13"
+catalog_since: "2026-07-18"
 
 # --- Resource hints (displayed on deploy screen) ---
 resources:

templates/uptime-kuma/docker-compose.yml

@@ -8,7 +8,7 @@
 
 services:
   uptime-kuma:
-    image: alpine:3.20
+    image: louislam/uptime-kuma:2.4.0
     container_name: uptime-kuma
     restart: unless-stopped
     environment: