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>

priv/repo/migrations/20260301133937_create_activity_log.exs

@@ -0,0 +1,102 @@
+defmodule Berrypod.Repo.Migrations.CreateActivityLog do
+  use Ecto.Migration
+
+  def up do
+    create table(:activity_log, primary_key: false) do
+      add :id, :binary_id, primary_key: true
+      add :event_type, :string, null: false
+      add :level, :string, null: false, default: "info"
+      add :order_id, references(:orders, type: :binary_id, on_delete: :nilify_all)
+      add :payload, :map, default: %{}
+      add :message, :string, null: false
+      add :resolved_at, :utc_datetime
+      add :occurred_at, :utc_datetime, null: false
+
+      timestamps(type: :utc_datetime)
+    end
+
+    create index(:activity_log, [:order_id])
+    create index(:activity_log, [:occurred_at])
+    create index(:activity_log, [:level, :resolved_at])
+
+    # Backfill from existing orders
+    flush()
+    backfill_from_orders()
+  end
+
+  def down do
+    drop table(:activity_log)
+  end
+
+  defp backfill_from_orders do
+    now = NaiveDateTime.utc_now() |> NaiveDateTime.truncate(:second)
+
+    # order.created for all paid orders
+    execute("""
+    INSERT INTO activity_log (id, event_type, level, order_id, payload, message, occurred_at, inserted_at, updated_at)
+    SELECT
+      lower(hex(randomblob(4)) || '-' || hex(randomblob(2)) || '-4' || substr(hex(randomblob(2)),2) || '-' || substr('89ab', abs(random()) % 4 + 1, 1) || substr(hex(randomblob(2)),2) || '-' || hex(randomblob(6))),
+      'order.created',
+      'info',
+      id,
+      '{}',
+      'Order placed',
+      inserted_at,
+      '#{now}',
+      '#{now}'
+    FROM orders
+    WHERE payment_status = 'paid'
+    """)
+
+    # order.submitted
+    execute("""
+    INSERT INTO activity_log (id, event_type, level, order_id, payload, message, occurred_at, inserted_at, updated_at)
+    SELECT
+      lower(hex(randomblob(4)) || '-' || hex(randomblob(2)) || '-4' || substr(hex(randomblob(2)),2) || '-' || substr('89ab', abs(random()) % 4 + 1, 1) || substr(hex(randomblob(2)),2) || '-' || hex(randomblob(6))),
+      'order.submitted',
+      'info',
+      id,
+      '{}',
+      'Submitted to provider',
+      submitted_at,
+      '#{now}',
+      '#{now}'
+    FROM orders
+    WHERE submitted_at IS NOT NULL
+    """)
+
+    # order.shipped
+    execute("""
+    INSERT INTO activity_log (id, event_type, level, order_id, payload, message, occurred_at, inserted_at, updated_at)
+    SELECT
+      lower(hex(randomblob(4)) || '-' || hex(randomblob(2)) || '-4' || substr(hex(randomblob(2)),2) || '-' || substr('89ab', abs(random()) % 4 + 1, 1) || substr(hex(randomblob(2)),2) || '-' || hex(randomblob(6))),
+      'order.shipped',
+      'info',
+      id,
+      '{}',
+      'Shipped',
+      shipped_at,
+      '#{now}',
+      '#{now}'
+    FROM orders
+    WHERE shipped_at IS NOT NULL
+    """)
+
+    # order.delivered
+    execute("""
+    INSERT INTO activity_log (id, event_type, level, order_id, payload, message, occurred_at, inserted_at, updated_at)
+    SELECT
+      lower(hex(randomblob(4)) || '-' || hex(randomblob(2)) || '-4' || substr(hex(randomblob(2)),2) || '-' || substr('89ab', abs(random()) % 4 + 1, 1) || substr(hex(randomblob(2)),2) || '-' || hex(randomblob(6))),
+      'order.delivered',
+      'info',
+      id,
+      '{}',
+      'Delivered',
+      delivered_at,
+      '#{now}',
+      '#{now}'
+    FROM orders
+    WHERE delivered_at IS NOT NULL
+    """)
+  end
+end