complete reviews system (phases 4-6)

- review display: photos with lightbox, verified badge, pagination
- admin moderation: pending/approved/rejected tabs, bulk actions, nav badge
- SEO: JSON-LD AggregateRating and Review markup on product pages
- automation: review request emails 7 days after delivery (Oban worker)
- rating cache: avg/count fields on products, updated on approval
- fix file size validation in media test (10MB limit)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

priv/repo/migrations/20260401221813_add_rating_cache_to_products.exs

@@ -0,0 +1,10 @@
+defmodule Berrypod.Repo.Migrations.AddRatingCacheToProducts do
+  use Ecto.Migration
+
+  def change do
+    alter table(:products) do
+      add :rating_avg, :decimal, precision: 2, scale: 1
+      add :rating_count, :integer, default: 0
+    end
+  end
+end