chore(tradein): browser-smoke.sh — verify tradein-browser /health + /fetch (#905)

Reusable smoke test for the camoufox HTTP service. Run from the deploy host:
  docker exec -i tradein-backend sh < tradein-mvp/scripts/browser-smoke.sh
Reports health, byte count, preloadedState presence, firewall-block detection
+ first 200 bytes of the response. Avoids long one-line curl commands that get
mangled on terminal paste.

Refs #905, #883

tradein-mvp/scripts/browser-smoke.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+# Smoke-test the tradein-browser service (camoufox HTTP wrapper, #905) from
+# inside the tradein docker network. Verifies /health and a real /fetch.
+#
+# Run from the deploy host (after `git pull`), piping the script into the
+# backend container (which shares the tradein-net with tradein-browser):
+#
+#   docker exec -i tradein-backend sh < tradein-mvp/scripts/browser-smoke.sh
+#
+# Override the target URL:
+#   URL=https://example.com docker exec -i -e URL tradein-backend sh < tradein-mvp/scripts/browser-smoke.sh
+set -eu
+
+B="${BROWSER_HTTP_ENDPOINT:-http://tradein-browser:3000}"
+U="${URL:-https://www.avito.ru/ekaterinburg/kvartiry/prodam}"
+
+printf 'health:    '
+curl -s --max-time 10 "$B/health" || echo "(no response)"
+echo
+
+echo "{\"url\":\"$U\"}" > /tmp/smoke_payload.json
+curl -s --max-time 120 -X POST "$B/fetch" \
+  -H 'Content-Type: application/json' \
+  -d @/tmp/smoke_payload.json \
+  -o /tmp/smoke_result.html || true
+
+echo "url:       $U"
+echo "bytes:     $(wc -c < /tmp/smoke_result.html 2>/dev/null || echo 0)"
+echo "preloaded: $(grep -c preloadedState /tmp/smoke_result.html 2>/dev/null || echo 0)"
+echo "firewall:  $(grep -ci firewall-container /tmp/smoke_result.html 2>/dev/null || echo 0)"
+echo "--- first 200 bytes (error JSON shows here if /fetch failed) ---"
+head -c 200 /tmp/smoke_result.html 2>/dev/null || true
+echo