Mark story 4-1 done, add deferred items from review

Review passed all criteria; update sprint-status to done, close the
story file, and record two deferred items (GPIO pins into constants.py,
ButtonHoldDetector init-time GPIO dependency) in deferred-work.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_bmad-output/implementation-artifacts/sprint-status.yaml

@@ -70,6 +70,6 @@ development_status:
 
   # Epic 4: Reset & Reconfiguration
   epic-4: in-progress
-  4-1-gpio-button-hold-detection-and-led-feedback: review
+  4-1-gpio-button-hold-detection-and-led-feedback: done
   4-2-config-wipe-setup-screen-and-return-to-provisioning: backlog
   epic-4-retrospective: optional