add activity log with order timeline and global feed

Single activity_log table powering two views: chronological timeline
on each order detail page (replacing the old fulfilment card) and a
global feed at /admin/activity with tabs, category filters, search,
and pagination. Real-time via PubSub — new entries appear instantly,
nav badge updates across all admin pages.

Instrumented across all event points: Stripe webhooks, order notifier,
submission worker, fulfilment status worker, product sync worker, and
Oban exhausted-job telemetry. Contextual action buttons (retry
submission, retry sync, dismiss) with Oban unique constraints to
prevent double-enqueue. 90-day pruning via cron.

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

assets/css/admin/components.css

@@ -2527,4 +2527,113 @@
   }
 }
 
+/* -- Timeline -- */
+
+.admin-timeline {
+  list-style: none;
+  padding: 0;
+  margin: 0;
+  position: relative;
+}
+
+.admin-timeline::before {
+  content: "";
+  position: absolute;
+  left: 0.4375rem;
+  top: 0.75rem;
+  bottom: 0.75rem;
+  width: 1px;
+  background: var(--t-border-default);
+}
+
+.admin-timeline-item {
+  display: flex;
+  gap: 0.75rem;
+  padding: 0.375rem 0;
+  position: relative;
+}
+
+.admin-timeline-dot {
+  width: 0.875rem;
+  height: 0.875rem;
+  border-radius: 9999px;
+  flex-shrink: 0;
+  margin-top: 0.125rem;
+  border: 2px solid var(--t-surface-base);
+  position: relative;
+  z-index: 1;
+}
+
+.admin-timeline-dot-info {
+  background: var(--t-status-success, #22c55e);
+}
+
+.admin-timeline-dot-warning {
+  background: var(--t-status-warning, #f59e0b);
+}
+
+.admin-timeline-dot-error {
+  background: var(--t-status-error, #ef4444);
+}
+
+.admin-timeline-content {
+  flex: 1;
+  min-width: 0;
+}
+
+.admin-timeline-message {
+  font-size: 0.875rem;
+  line-height: 1.4;
+  margin: 0;
+}
+
+.admin-timeline-time {
+  font-size: 0.75rem;
+  color: color-mix(in oklch, var(--t-text-primary) 50%, transparent);
+}
+
+/* -- Activity feed -- */
+
+.admin-activity-row {
+  display: flex;
+  align-items: flex-start;
+  gap: 0.75rem;
+  padding: 0.625rem 0;
+  border-bottom: 1px solid color-mix(in oklch, var(--t-border-default) 50%, transparent);
+}
+
+.admin-activity-row:last-child {
+  border-bottom: none;
+}
+
+.admin-activity-icon {
+  flex-shrink: 0;
+  margin-top: 0.125rem;
+}
+
+.admin-activity-body {
+  flex: 1;
+  min-width: 0;
+  font-size: 0.875rem;
+  line-height: 1.4;
+}
+
+.admin-activity-type {
+  font-weight: 500;
+  margin-right: 0.25rem;
+}
+
+.admin-activity-meta {
+  flex-shrink: 0;
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+}
+
+.admin-activity-time {
+  font-size: 0.75rem;
+  color: color-mix(in oklch, var(--t-text-primary) 50%, transparent);
+  white-space: nowrap;
+}
+
 } /* @layer admin */