test: add comprehensive dockerised end-to-end suite

Add a black-box e2e suite (build tag dockere2e) that runs against the
built container image via docker-compose, plus a static nginx mock
upstream for hermetic caching tests.

Coverage:
- repository add/change/delete for remote, local and virtual repos
- caching (miss -> hit + byte integrity) for all 10 remote package types
- local uploads: generic, pypi (with generated simple index), rpm (with
  automatic repodata generation from a real package)
- virtual merges: pypi simple index and helm index.yaml

Driven by scripts/docker-e2e.sh (make docker-e2e): builds the image,
brings the stack up, waits for health, runs the suite, and tears down.
The artifactapi host port is parameterised (ARTIFACTAPI_PORT, default
8000; the e2e run uses 8001). Fixtures are force-tracked over the global
gitignore.

scripts/docker-e2e.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Build the artifactapi container, bring up the full stack (postgres, redis,
+# minio, artifactapi) plus a static mock upstream, and run the dockerised e2e
+# suite against the running product over HTTP. Tears everything down on exit.
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+# Publish artifactapi on 8001 to avoid colliding with a local instance on 8000.
+export ARTIFACTAPI_PORT="${ARTIFACTAPI_PORT:-8001}"
+COMPOSE=(docker compose -f docker-compose.yml -f docker-compose.e2e.yml)
+API_URL="${ARTIFACTAPI_URL:-http://localhost:${ARTIFACTAPI_PORT}}"
+
+cleanup() {
+  echo "==> tearing down stack"
+  "${COMPOSE[@]}" down -v --remove-orphans >/dev/null 2>&1 || true
+}
+trap cleanup EXIT
+
+echo "==> building and starting stack (postgres, redis, minio, mockupstream, artifactapi)"
+"${COMPOSE[@]}" up -d --build postgres redis minio mockupstream artifactapi
+
+echo "==> waiting for artifactapi health at ${API_URL}"
+for i in $(seq 1 60); do
+  if curl -fsS "${API_URL}/health" >/dev/null 2>&1; then
+    echo "    healthy after ${i}s"
+    break
+  fi
+  if [ "$i" -eq 60 ]; then
+    echo "!!! artifactapi did not become healthy in time; recent logs:"
+    "${COMPOSE[@]}" logs --tail=50 artifactapi
+    exit 1
+  fi
+  sleep 1
+done
+
+echo "==> running dockerised e2e suite"
+ARTIFACTAPI_URL="${API_URL}" \
+MOCK_UPSTREAM_INTERNAL="${MOCK_UPSTREAM_INTERNAL:-http://mockupstream}" \
+  go test -tags=dockere2e -count=1 -timeout=10m -v ./e2e-docker/...