fix: edge container — add python3, fix mktemp BusyBox compat

Dockerfile: caddy:latest is Alpine, needs apk not apt-get. Add python3
which dispatcher.sh requires for JSON filtering since Apr 6.

dispatcher.sh: BusyBox mktemp does not support suffixes after XXXXXX
template. Remove .txt suffix.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker/edge/Dockerfile

@@ -1,4 +1,4 @@
 FROM caddy:latest
-RUN apt-get update && apt-get install -y bash jq curl git docker.io && rm -rf /var/lib/apt/lists/*
+RUN apk add --no-cache bash jq curl git docker-cli python3
 COPY entrypoint-edge.sh /usr/local/bin/entrypoint-edge.sh
 ENTRYPOINT ["bash", "/usr/local/bin/entrypoint-edge.sh"]

docker/edge/dispatcher.sh

@@ -462,7 +462,7 @@ launch_runner() {
 
   # Create temp file for logs
   local log_file
-  log_file=$(mktemp /tmp/dispatcher-logs-XXXXXX.txt)
+  log_file=$(mktemp /tmp/dispatcher-logs-XXXXXX)
   trap 'rm -f "$log_file"' RETURN
 
   # Execute with array expansion (safe from shell injection)