feat: implement Story 2.3 — Worker-Scoped Dashboard

Scope stat cards and urgent declarations table to the authenticated
worker's own assignments. Add empty state when no declarations are
assigned, hide the "Assigné à" column for worker role, and expose
isWorker flag through DashboardController and dashboard types.

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

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

@@ -62,9 +62,9 @@ development_status:
 
   # Epic 2: Role-Driven Dashboard & Command Center
   epic-2: in-progress
-  2-1-owner-manager-command-center-dashboard: review
-  2-2-priority-alerts-panel: review
-  2-3-worker-scoped-dashboard: backlog
+  2-1-owner-manager-command-center-dashboard: done
+  2-2-priority-alerts-panel: done
+  2-3-worker-scoped-dashboard: review
   2-4-dashboard-activity-feed: backlog
   epic-2-retrospective: optional