add privacy-first analytics with progressive event collection

Three-layer pipeline: Plug for all HTTP requests (no JS needed), LiveView
hook for SPA navigations, JS hook for screen width. ETS-backed buffer
batches writes to SQLite every 10s. Daily-rotating salt for visitor hashing.
Includes admin dashboard with date ranges, visitor trends, top pages,
sources, devices, and e-commerce conversion funnel. Oban cron for 12-month
data retention.

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

lib/berrypod_web/live/shop/checkout_success.ex

@@ -1,7 +1,7 @@
 defmodule BerrypodWeb.Shop.CheckoutSuccess do
   use BerrypodWeb, :live_view
 
-  alias Berrypod.Orders
+  alias Berrypod.{Analytics, Orders}
 
   @impl true
   def mount(%{"session_id" => session_id}, _session, socket) do
@@ -12,6 +12,15 @@ defmodule BerrypodWeb.Shop.CheckoutSuccess do
       Phoenix.PubSub.subscribe(Berrypod.PubSub, "order:#{order.id}:status")
     end
 
+    # Track purchase event
+    if order && connected?(socket) && socket.assigns[:analytics_visitor_hash] do
+      Analytics.track_event("purchase", %{
+        pathname: "/checkout/success",
+        visitor_hash: socket.assigns.analytics_visitor_hash,
+        revenue: order.total
+      })
+    end
+
     # Clear the cart after successful checkout
     socket =
       if order && connected?(socket) do

lib/berrypod_web/live/shop/product_show.ex

@@ -1,7 +1,7 @@
 defmodule BerrypodWeb.Shop.ProductShow do
   use BerrypodWeb, :live_view
 
-  alias Berrypod.Cart
+  alias Berrypod.{Analytics, Cart}
   alias Berrypod.Images.Optimizer
   alias Berrypod.Products
   alias Berrypod.Products.{Product, ProductImage}
@@ -41,6 +41,13 @@ defmodule BerrypodWeb.Shop.ProductShow do
         display_price = variant_price(selected_variant, product)
         gallery_images = filter_gallery_images(all_images, selected_options["Color"])
 
+        if connected?(socket) and socket.assigns[:analytics_visitor_hash] do
+          Analytics.track_event("product_view", %{
+            pathname: "/products/#{slug}",
+            visitor_hash: socket.assigns.analytics_visitor_hash
+          })
+        end
+
         socket =
           socket
           |> assign(:page_title, product.title)
@@ -177,6 +184,13 @@ defmodule BerrypodWeb.Shop.ProductShow do
     if variant do
       cart = Cart.add_item(socket.assigns.raw_cart, variant.id, socket.assigns.quantity)
 
+      if socket.assigns[:analytics_visitor_hash] do
+        Analytics.track_event("add_to_cart", %{
+          pathname: "/products/#{socket.assigns.product.slug}",
+          visitor_hash: socket.assigns.analytics_visitor_hash
+        })
+      end
+
       socket =
         socket
         |> BerrypodWeb.CartHook.broadcast_and_update(cart)