test(docker): add hermetic /api proxy smoke test

make smoke-docker builds the image, stands up a stub upstream + the container
on a shared network, and asserts forward+prefix-strip, upstream-header cleared,
421 on missing header, and 403 + reject sentinel on allowlist miss. Self-
contained (no tailnet), idempotent, local-only (Docker) like cargo-check.

docker/smoke-test.sh

@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+# Hermetic container smoke test for the same-origin /api proxy.
+#
+# Builds the image, then stands up a stub upstream + the openconcho container on
+# a shared Docker network and asserts the proxy forwards correctly. Fully
+# self-contained — no external Honcho or tailnet needed. Local-only (requires a
+# Docker daemon); not part of PR CI, like the desktop cargo-check preflight.
+#
+# Idempotent: removes its own containers/network on entry and exit. Exits non-zero
+# on any failed assertion.
+#
+# Usage: make smoke-docker   (or: bash docker/smoke-test.sh)
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+IMAGE="openconcho-web:smoke"
+NET="oc-smoke-net"
+UPSTREAM="oc-smoke-upstream"
+APP="oc-smoke-app"
+PORT="${SMOKE_PORT:-18080}"
+# Echo server: returns request method/path/headers as JSON for any verb.
+STUB_IMAGE="mendhak/http-https-echo:31"
+FAIL=0
+
+cleanup() {
+	docker rm -f "$APP" "$UPSTREAM" >/dev/null 2>&1 || true
+	docker network rm "$NET" >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+cleanup
+
+wait_ready() { # url
+	for _ in $(seq 1 30); do
+		curl -fsS "$1" >/dev/null 2>&1 && return 0
+		sleep 0.5
+	done
+	echo "  FAIL: container did not become ready at $1"
+	FAIL=1
+}
+
+check() { # label expected actual
+	if [ "$2" = "$3" ]; then echo "  PASS: $1 ($3)"; else echo "  FAIL: $1 — expected $2, got $3"; FAIL=1; fi
+}
+
+echo "==> build image"
+docker build -t "$IMAGE" . >/dev/null
+
+echo "==> create network + stub upstream"
+docker network create "$NET" >/dev/null
+docker run -d --name "$UPSTREAM" --network "$NET" -e HTTP_PORT=8080 "$STUB_IMAGE" >/dev/null
+
+echo "==> start openconcho (default-open allowlist)"
+docker run -d --name "$APP" --network "$NET" -p "$PORT:8080" \
+	-e "OPENCONCHO_DEFAULT_HONCHO_URL=http://$UPSTREAM:8080" "$IMAGE" >/dev/null
+wait_ready "http://localhost:$PORT/healthz"
+
+echo "==> assertions"
+check "healthz 200" 200 "$(curl -s -o /dev/null -w '%{http_code}' "http://localhost:$PORT/healthz")"
+check "SPA served 200" 200 "$(curl -s -o /dev/null -w '%{http_code}' "http://localhost:$PORT/")"
+check "config.js injected" 200 "$(curl -s -o /dev/null -w '%{http_code}' "http://localhost:$PORT/config.js")"
+
+# Proxy forwards POST /api/v3/test -> stub, stripping the /api prefix.
+body=$(curl -s "http://localhost:$PORT/api/v3/test" \
+	-H "X-Honcho-Upstream: http://$UPSTREAM:8080" -H 'content-type: application/json' -X POST -d '{}')
+if echo "$body" | grep -q '/v3/test'; then echo "  PASS: /api forwards + strips prefix"; else echo "  FAIL: forward/strip — body: $body"; FAIL=1; fi
+# Routing header must NOT leak to the upstream.
+if echo "$body" | grep -qi 'x-honcho-upstream'; then echo "  FAIL: X-Honcho-Upstream leaked upstream"; FAIL=1; else echo "  PASS: X-Honcho-Upstream cleared upstream"; fi
+# Missing routing header -> 421.
+check "missing header 421" 421 "$(curl -s -o /dev/null -w '%{http_code}' "http://localhost:$PORT/api/v3/test" -X POST -d '{}')"
+
+echo "==> restart with a non-matching allowlist"
+docker rm -f "$APP" >/dev/null
+docker run -d --name "$APP" --network "$NET" -p "$PORT:8080" \
+	-e "OPENCONCHO_UPSTREAM_ALLOWLIST=*.honcho.dev" "$IMAGE" >/dev/null
+wait_ready "http://localhost:$PORT/healthz"
+check "allowlist reject 403" 403 "$(curl -s -o /dev/null -w '%{http_code}' "http://localhost:$PORT/api/v3/test" \
+	-H "X-Honcho-Upstream: http://$UPSTREAM:8080" -X POST -d '{}')"
+reject=$(curl -s -D- -o /dev/null "http://localhost:$PORT/api/v3/test" \
+	-H "X-Honcho-Upstream: http://$UPSTREAM:8080" -X POST -d '{}' | grep -i 'X-Honcho-Proxy-Reject' | tr -d '\r')
+if echo "$reject" | grep -qi 'allowlist'; then echo "  PASS: reject sentinel header present"; else echo "  FAIL: missing reject sentinel — got: $reject"; FAIL=1; fi
+
+if [ "$FAIL" = 0 ]; then echo "==> SMOKE TEST PASSED"; else echo "==> SMOKE TEST FAILED"; exit 1; fi