Ship the extension as a signed CRX from our own update server

The dashboard-hosting stack from the previous commit is gone; it was answering
a question nobody asked. What was actually needed is Chrome's real update
channel, which an unpacked extension does not have and cannot be given.

So the extension is now signed into a CRX with an update manifest beside it,
served from the droplet, and installed on the trading machines by policy
(ExtensionInstallForcelist). From there Chrome installs it, updates it on its
own schedule, and puts it back if it goes missing. The manifest gained the
`key` that fixes the extension id, so an unpacked development load keeps the
same identity as the published build.

The self-update check now branches on how it was installed: policy installs ask
Chrome to check the update server now rather than waiting out its five-hour
cycle, and unpacked loads keep the reload-from-disk path. chrome.management
.getSelf() tells the two apart and needs no permission to do it.

The signing key lives at /opt/autofirmer-updates/key.pem on the droplet and
nowhere else. It is the extension's identity: a different key is a different
extension, and no browser would take it as an update.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

deploy/bootstrap-tls.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# First run only: get a certificate for FIRMER_HOST, then hand off to deploy.sh.
+# First run only: get a certificate for EXT_HOST, then hand off to deploy.sh.
 #
 # This uses the autotrader stack's certbot container and its Let's Encrypt
 # account, so it agrees to the Subscriber Agreement the same way that stack's
@@ -13,7 +13,7 @@ fail() { printf '\n\033[1;31mERROR: %s\033[0m\n' "$1" >&2; exit 1; }
 
 [ -f .env ] || fail "no .env — copy .env.example to .env and fill it in"
 set -a; . ./.env; set +a
-: "${FIRMER_HOST:?set FIRMER_HOST in .env}"
+: "${EXT_HOST:?set EXT_HOST in .env}"
 SHARED_STACK="${SHARED_STACK:-/opt/autotrader/deploy}"
 
 # ACME_EMAIL is not duplicated here: it belongs to the account that already
@@ -27,24 +27,24 @@ log "Checking DNS"
 ip=$(curl -fsS --max-time 5 http://169.254.169.254/metadata/v1/interfaces/public/0/ipv4/address 2>/dev/null \
      || curl -fsS --max-time 5 https://api.ipify.org 2>/dev/null) \
     || fail "could not determine this droplet's public IP"
-got=$(getent ahostsv4 "$FIRMER_HOST" 2>/dev/null | awk 'NR==1{print $1}') || true
-echo "  droplet:      $ip"
-echo "  $FIRMER_HOST -> ${got:-<unresolved>}"
-[ "$got" = "$ip" ] || fail "$FIRMER_HOST does not resolve to $ip — fix DNS and wait for it to propagate"
+got=$(getent ahostsv4 "$EXT_HOST" 2>/dev/null | awk 'NR==1{print $1}') || true
+echo "  droplet:   $ip"
+echo "  $EXT_HOST -> ${got:-<unresolved>}"
+[ "$got" = "$ip" ] || fail "$EXT_HOST does not resolve to $ip — fix DNS and wait for it to propagate"
 
 # The challenge is served over plain HTTP by the shared nginx, which needs a
 # server block for this name before it will answer for it.
 log "Rendering the HTTP-only config so the challenge can be served"
-envsubst '${FIRMER_HOST}' < nginx/firmer-acme.conf.template > "$SHARED_STACK/nginx/conf.d/firmer.conf"
+envsubst '${EXT_HOST}' < nginx/ext-acme.conf.template > "$SHARED_STACK/nginx/conf.d/ext.conf"
 docker exec nginx nginx -t
 docker exec nginx nginx -s reload
 
-log "Requesting a certificate for $FIRMER_HOST"
+log "Requesting a certificate for $EXT_HOST"
 docker compose --project-directory "$SHARED_STACK" -f "$SHARED_STACK/docker-compose.yml" \
     run --rm --entrypoint certbot certbot \
     certonly --webroot -w /var/www/certbot \
     --email "$ACME_EMAIL" --agree-tos --no-eff-email \
-    --non-interactive -d "$FIRMER_HOST" \
+    --non-interactive -d "$EXT_HOST" \
     || fail "certbot failed — check DNS and that port 80 reaches this droplet"
 
 log "Switching to the TLS config"