Upgrade to Alpine 3.20 (and bump everything else too)

I thought this would automatically bump me to LLVM 18, but the plain
"clang" package points to "clang17" as of this writing. Maybe I'll try
Clang 18 myself in a future change.

ESLint 9.x is out, but requires migrating my existing configuration.
I guess I can deal with that the next time I'm *really* bored.

Dockerfile

@@ -1,12 +1,12 @@
-# syntax = docker.io/docker/dockerfile:1.6
+# syntax = docker.io/docker/dockerfile:1.7
 
 # The Alpine and Go base images must use the same release of Alpine.
-ARG ALPINE_BASE=docker.io/library/alpine:3.19
-ARG GOLANG_BASE=docker.io/library/golang:1.22-alpine3.19
+ARG ALPINE_BASE=docker.io/library/alpine:3.20
+ARG GOLANG_BASE=docker.io/library/golang:1.22-alpine3.20
 # The Node.js image does not require any particular OS.
-ARG NODEJS_BASE=docker.io/library/node:20-alpine
-# See https://gstreamer.freedesktop.org/download/.
-ARG GSTREAMER_VERSION=1.24.2
+ARG NODEJS_BASE=docker.io/library/node:22-alpine
+# See https://gstreamer.freedesktop.org/news/.
+ARG GSTREAMER_VERSION=1.24.3
 
 
 # Let's get the client build out of the way, since it's much simpler than