feat(storage-minio): initial implementation — MinIO/S3 object storage with lifecycle (v1.0.0)

Introduces code.nochebuena.dev/einherjar/storage-minio — the object storage
starter for the Einherjar framework. Absorbs the minio package from micro-lib,
replacing fmt.Errorf wrapping with core/xerrors.

Interfaces (CT-6: one TypeSpec per file):
- Provider — PutObject, RemoveObject, GetObject, PresignedGetObject, HandleError
- Component — lifecycle.Component + observability.Checkable + Provider + Native()

Implementation:
- New(logger, cfg) Component — client not created until OnInit
- OnInit: minio.New with credentials and transport; bucket existence check
- OnStart: BucketExists PING; logs "minio: connected"
- OnStop: logs "minio: closing client" (minio-go is stateless; no explicit close)
- HealthCheck: BucketExists check; Priority LevelCritical
- Native() *miniogo.Client — escape hatch for operations not in Provider
- HandleError: maps minio-go errors to xerrors (NotFound, AlreadyExists, Internal)

Config (EINHERJAR_MINIO_* env vars):
  Endpoint(required), AccessKey(required), SecretKey(required),
  Bucket(required), UseSSL(false), Region(us-east-1)

- Component interface embeds observability.Identifiable; identifiable.go implements
  ModulePath and ModuleVersion via runtime/debug.ReadBuildInfo() — prints in launcher banner

errors.go

@@ -0,0 +1,27 @@
+package minio
+
+import (
+	miniogo "github.com/minio/minio-go/v7"
+
+	"code.nochebuena.dev/einherjar/core/xerrors"
+)
+
+// HandleError maps minio-go errors to xerrors types.
+// Also available as client.HandleError(err).
+func HandleError(err error) error {
+	if err == nil {
+		return nil
+	}
+	resp := miniogo.ToErrorResponse(err)
+	switch resp.Code {
+	case miniogo.NoSuchBucket:
+		return xerrors.NotFound("bucket not found").WithError(err)
+	case miniogo.NoSuchKey:
+		return xerrors.NotFound("object not found").WithError(err)
+	case miniogo.AccessDenied, miniogo.InvalidAccessKeyID:
+		return xerrors.PermissionDenied("access denied").WithError(err)
+	case miniogo.BucketAlreadyExists, miniogo.BucketAlreadyOwnedByYou:
+		return xerrors.AlreadyExists("bucket already exists").WithError(err)
+	}
+	return xerrors.Internal("unexpected storage error").WithError(err)
+}