test(integration): reorganize test structure and add runner script

- Move integration tests and mock upstream resources from `integration/` to `test/` directory.
- Add `test/integration.sh` script to orchestrate environment setup and test execution.
- Update build context in `docker-compose.integration.yml` to match new structure.
- Add documentation for local development and integration testing workflows in README.

test/integration.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Runs integration tests inside the ez-api repo (builds docker-compose + go test).
+
+REPO_ROOT=$(cd -- "$(dirname -- "$0")"/.. && pwd)
+compose_file="$REPO_ROOT/docker-compose.integration.yml"
+
+echo "[integration] bringing up services..."
+docker compose -f "$compose_file" up --build -d --wait
+
+cleanup() {
+  echo "[integration] tearing down services..."
+  docker compose -f "$compose_file" down -v
+}
+trap cleanup EXIT
+
+echo "[integration] running go test with integration tag..."
+cd "$REPO_ROOT/test"
+go test -tags=integration ./...