feat: add notification center with bell dropdown, full page, and workspace scoping (Story 3.3)

Enhance NotificationDropdown with type-specific icons, French description builder,
click-to-navigate with mark-as-read, and "Voir toutes les notifications" link.
Add full notifications page at /notifications with pagination (25/page), individual
mark-as-read, and empty state. Includes code review fixes: workspace-scoped unread
count and dropdown items, race condition fix (mark-as-read before navigate),
efficient markAllAsRead via direct update, deleted declaration URL handling,
and per-workspace cache keys. 7 new feature tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -34,7 +34,7 @@
 # - Dev moves story to 'review', then runs code-review (fresh context, different LLM recommended)
 
 generated: 2026-03-11
-last_updated: 2026-03-24T00:00:00
+last_updated: "2026-03-26"
 project: "l'ami fiduciaire"
 project_key: NOKEY
 tracking_system: file-system
@@ -69,10 +69,10 @@ development_status:
   epic-2-retrospective: done
 
   # Epic 3: Collaboration, Nudge System & Notifications
-  epic-3: backlog
-  3-1-notification-infrastructure-setup: backlog
-  3-2-one-click-nudge-system: backlog
-  3-3-notification-center-and-bell: backlog
+  epic-3: in-progress
+  3-1-notification-infrastructure-setup: done
+  3-2-one-click-nudge-system: done
+  3-3-notification-center-and-bell: review
   3-4-bulk-client-notification-scheduling: backlog
   3-5-email-notification-enhancement-for-key-events: backlog
   epic-3-retrospective: optional