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>

test/berrypod_web/live/admin/orders_test.exs

@@ -116,12 +116,12 @@ defmodule BerrypodWeb.Admin.OrdersTest do
         live(conn, ~p"/admin/orders/#{fake_id}")
     end
 
-    test "shows fulfilment card", %{conn: conn} do
+    test "shows timeline card", %{conn: conn} do
       order = order_fixture(payment_status: "paid")
 
       {:ok, _view, html} = live(conn, ~p"/admin/orders/#{order}")
 
-      assert html =~ "Fulfilment"
+      assert html =~ "Timeline"
       assert html =~ "unfulfilled"
     end
 
@@ -172,6 +172,49 @@ defmodule BerrypodWeb.Admin.OrdersTest do
     end
   end
 
+  describe "order timeline" do
+    setup %{conn: conn, user: user} do
+      conn = log_in_user(conn, user)
+      %{conn: conn}
+    end
+
+    test "renders timeline entries for an order", %{conn: conn} do
+      order = order_fixture(payment_status: "paid")
+
+      Berrypod.ActivityLog.log_event("order.created", "Order placed", order_id: order.id)
+
+      Berrypod.ActivityLog.log_event("order.submitted", "Submitted to provider",
+        order_id: order.id
+      )
+
+      {:ok, _view, html} = live(conn, ~p"/admin/orders/#{order}")
+
+      assert html =~ "Order placed"
+      assert html =~ "Submitted to provider"
+    end
+
+    test "shows empty state when no timeline entries", %{conn: conn} do
+      order = order_fixture(payment_status: "paid")
+
+      {:ok, _view, html} = live(conn, ~p"/admin/orders/#{order}")
+
+      assert html =~ "No activity recorded yet"
+    end
+
+    test "updates timeline via PubSub", %{conn: conn} do
+      order = order_fixture(payment_status: "paid")
+
+      {:ok, view, _html} = live(conn, ~p"/admin/orders/#{order}")
+
+      Berrypod.ActivityLog.log_event("order.submitted", "Submitted to provider",
+        order_id: order.id
+      )
+
+      html = render(view)
+      assert html =~ "Submitted to provider"
+    end
+  end
+
   describe "order list fulfilment column" do
     setup %{conn: conn, user: user} do
       conn = log_in_user(conn, user)