feat(01-03): move create_vo_backend factory into components/vio/factory.py

- Lift the env-aware VO backend factory verbatim from core/vo.py.
- Body and parameter defaults preserved exactly (PATTERNS.md §4.1
  mandate: 'Preserve this factory verbatim').
- Return-type annotation widened from ISequentialVisualOdometry to the
  canonical VisualOdometry Protocol from Plan 01-02; the I-prefix alias
  is still importable so legacy callers/type-checkers keep working.
- Imports route through the new components.vio.* modules; no
  cross-package edits needed because Plan 08 (composition root) is the
  only other call site planned.
- Append to the components.vio barrel.

src/gps_denied/components/vio/__init__.py

@@ -24,6 +24,7 @@ from gps_denied.components.vio.cuvslam_backend import (
     CuVSLAMMonoDepthVisualOdometry,
     CuVSLAMVisualOdometry,
 )
+from gps_denied.components.vio.factory import create_vo_backend
 
 __all__ = [
     "VisualOdometry",
@@ -32,4 +33,5 @@ __all__ = [
     "SequentialVisualOdometry",
     "CuVSLAMVisualOdometry",
     "CuVSLAMMonoDepthVisualOdometry",
+    "create_vo_backend",
 ]