feat: comprehensive Makefile overhaul with self-contained test targets, OpenAPI spec, and bug fixes

- Makefile: 16 test targets (test-unit, test-bdd, test-integration, test-conformance,
  test-concurrency, test-migration, test-api, test-ldap, test-vault, test-oidc,
  test-auth, test-compatibility) with BACKEND= variable support and auto-detected
  container runtime (docker/podman)
- Helper scripts: start-db.sh, stop-db.sh, setup-ldap.sh, setup-vault.sh, setup-oidc.sh
  for Docker lifecycle management with sr-test-* container naming
- OpenAPI spec: complete 3100+ line spec with embedded serving at /docs endpoint
- Fix LDAP bootstrap.ldif: reorder users before groups so memberOf overlay works
- Fix migrate-from-confluent.sh: empty array expansion with set -u, container networking
- Fix concurrency test port conflict: 18081 → 28181 to avoid BDD container collision
- Fix migration test: dedicated container network for Podman macOS compatibility

Author: millerjp

.gitignore

@@ -32,6 +32,9 @@ config.local.yaml
 .env
 .env.local
 
+# Generated API documentation
+docs/api/
+
 # Debug
 debug
 *.log

Makefile

@@ -0,0 +1,9 @@
+// Package api provides embedded API specification assets.
+package api
+
+import _ "embed"
+
+// OpenAPISpec contains the embedded OpenAPI 3.0 specification.
+//
+//go:embed openapi.yaml
+var OpenAPISpec []byte