feat: implement Story 2.4 — Dashboard Activity Feed with review fixes

Add role-scoped activity feed to the dashboard showing the 20 most recent
workspace events. Owners/Managers see all activity (declarations, clients,
team changes); Workers see only their assigned declarations. Includes
French descriptions, relative timestamps, responsive layout (desktop
sidebar, tablet inline, mobile collapsible), and 7 passing Pest tests.

Review fixes applied: batch-load declarations/clients/users to eliminate
N+1 queries, consistent soft-delete handling in URL resolution, French
grammar singular/plural fix, missing icon map entry, and corrected tablet
breakpoint per spec.

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

resources/js/composables/useRelativeTime.ts

@@ -0,0 +1,43 @@
+export function formatRelativeTime(isoTimestamp: string): string {
+    const date = new Date(isoTimestamp);
+    const now = new Date();
+    const diffMs = now.getTime() - date.getTime();
+    const diffMinutes = Math.floor(diffMs / (1000 * 60));
+    const diffHours = Math.floor(diffMs / (1000 * 60 * 60));
+    const diffDays = Math.floor(diffMs / (1000 * 60 * 60 * 24));
+
+    if (diffMinutes < 1) {
+        return "à l'instant";
+    }
+
+    if (diffMinutes < 60) {
+        return `il y a ${diffMinutes} min`;
+    }
+
+    if (diffHours < 24) {
+        return `il y a ${diffHours} h`;
+    }
+
+    const yesterday = new Date(now);
+    yesterday.setDate(yesterday.getDate() - 1);
+    if (
+        date.getDate() === yesterday.getDate() &&
+        date.getMonth() === yesterday.getMonth() &&
+        date.getFullYear() === yesterday.getFullYear()
+    ) {
+        return 'hier';
+    }
+
+    if (diffDays < 7) {
+        return `il y a ${diffDays} ${diffDays === 1 ? 'jour' : 'jours'}`;
+    }
+
+    const day = String(date.getDate()).padStart(2, '0');
+    const month = String(date.getMonth() + 1).padStart(2, '0');
+    const year = date.getFullYear();
+    return `${day}/${month}/${year}`;
+}
+
+export function useRelativeTime() {
+    return { formatRelativeTime };
+}