fix(FN-789): fix activity log data loading and restore modal styling

- Fix useActivityLog hook to properly load activity log entries from the store
- Add comprehensive test coverage for useActivityLog hook with 243 lines of tests
- Restore missing ActivityLogModal CSS styles (modal overlay, list, animations)
- Add ActivityLogModal component tests for empty state, loading, and error handling
- Register activity log route in App.tsx
- Update README with activity log data source documentation
- Add changeset for patch release

packages/dashboard/app/styles.css

@@ -12143,6 +12143,65 @@ html .column.drag-over * {
   }
 }
 
+/* Active filters bar */
+.activity-log-active-filters {
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm);
+  padding: var(--space-sm) 20px;
+  border-bottom: 1px solid var(--border);
+  background: var(--bg-secondary);
+  flex-wrap: wrap;
+}
+
+.activity-log-filter-label {
+  font-size: 12px;
+  color: var(--text-muted);
+  font-weight: 500;
+}
+
+.activity-log-filter-badge {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  padding: 2px 8px;
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: var(--radius-pill);
+  color: var(--text-muted);
+  font-size: 11px;
+  font-weight: 600;
+}
+
+.activity-log-clear-filters {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  padding: 2px 8px;
+  margin-left: auto;
+  background: none;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-sm);
+  color: var(--text-muted);
+  font-size: 11px;
+  cursor: pointer;
+  transition:
+    background var(--transition-fast),
+    color var(--transition-fast),
+    border-color var(--transition-fast);
+}
+
+.activity-log-clear-filters:hover {
+  background: var(--card-hover);
+  color: var(--text);
+  border-color: var(--text-dim);
+}
+
+/* Project filter variant */
+.activity-log-filter--project {
+  min-width: 140px;
+}
+
 /* Confirmation dialog */
 .activity-log-confirm-overlay {
   position: absolute;