dev-updater: build an app on the machine, install it on the phone

A Rust backend that discovers Android projects under configured roots,
builds one on request, and serves the APK over pinned TLS on a WireGuard
interface; an Android client that lists what is buildable, watches a build,
and installs the result. Enrolment carries the token and the CA, so the
phone trusts exactly the machine that issued it and nothing else.

`AGENTS.md` is the working guide and `README.md` the configuration
reference. The shared tunnel-and-TLS code lives in `vendor/wg-app-link`,
which ai-app uses too.

History before this point was squashed away, and a stale `config.json` went
with it: nothing had read that file since the config moved to RON outside
the checkout, and what it still held was one machine's absolute paths and
the names of projects on it.

test-projects/service-and-app/build-daemon.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+# "Builds" this project's daemon, which is a shell script and so needs no
+# building at all. What it actually does is take a few seconds and report
+# progress, because that is the thing worth having: a component slow enough
+# to watch a bar move on, next to an APK component that finishes in two
+# seconds. A card with one instant component and one slow one is how you see
+# whether the per-component timings and the concurrent build really are per
+# component.
+set -eu
+
+STEPS=8
+i=0
+while [ "$i" -lt "$STEPS" ]; do
+    i=$((i + 1))
+    echo "@@progress $i/$STEPS"
+    echo "==> Pretending to compile part $i of $STEPS"
+    sleep 1
+done
+
+chmod +x ./serve.sh
+echo "==> Daemon ready"