add analytics CSV export

Downloads a ZIP with one CSV per report (overview, trend, pages, entry/exit
pages, sources, referrers, countries, devices, funnel). Export button lives
next to the period selector and picks up the current period and any active
filters using a JS hook + JS.set_attribute, so the downloaded data always
matches what's on screen.

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

lib/berrypod_web/live/admin/analytics.ex

@@ -144,15 +144,30 @@ defmodule BerrypodWeb.Admin.Analytics do
     <.header>Analytics</.header>
 
     <%!-- Period selector --%>
-    <div class="analytics-periods" style="display: flex; gap: 0.25rem; margin-top: 1rem;">
+    <div
+      class="analytics-periods"
+      style="display: flex; gap: 0.25rem; margin-top: 1rem; align-items: center;"
+    >
       <button
         :for={period <- ["today", "7d", "30d", "12m"]}
-        phx-click="change_period"
-        phx-value-period={period}
+        phx-click={
+          JS.push("change_period", value: %{period: period})
+          |> JS.set_attribute({"data-period", period}, to: "#analytics-export-link")
+        }
         class={["admin-btn admin-btn-sm", @period == period && "admin-btn-primary"]}
       >
         {period_label(period)}
       </button>
+      <a
+        id="analytics-export-link"
+        data-period={@period}
+        href={export_url(@period, @filters)}
+        class="admin-btn admin-btn-sm"
+        style="margin-left: auto;"
+        phx-hook="AnalyticsExport"
+      >
+        Export CSV
+      </a>
     </div>
 
     <%!-- Active filters --%>
@@ -308,7 +323,11 @@ defmodule BerrypodWeb.Admin.Analytics do
     assigns = assign(assigns, label: filter_label(assigns.dimension, assigns.value))
 
     ~H"""
-    <span style="display: inline-flex; align-items: center; gap: 0.25rem; padding: 0.25rem 0.5rem; font-size: 0.75rem; background: var(--color-base-200, #e5e5e5); border-radius: 0.25rem;">
+    <span
+      data-filter-dimension={@dimension}
+      data-filter-value={@value}
+      style="display: inline-flex; align-items: center; gap: 0.25rem; padding: 0.25rem 0.5rem; font-size: 0.75rem; background: var(--color-base-200, #e5e5e5); border-radius: 0.25rem;"
+    >
       {@label}
       <button
         phx-click="remove_filter"
@@ -745,6 +764,15 @@ defmodule BerrypodWeb.Admin.Analytics do
   defp period_label("30d"), do: "30 days"
   defp period_label("12m"), do: "12 months"
 
+  defp export_url(period, filters) do
+    params =
+      Enum.reduce(filters, %{"period" => period}, fn {k, v}, acc ->
+        Map.put(acc, "filter[#{k}]", v)
+      end)
+
+    "/admin/analytics/export?" <> URI.encode_query(params)
+  end
+
   defp format_number(n) when n >= 1_000_000, do: "#{Float.round(n / 1_000_000, 1)}M"
   defp format_number(n) when n >= 1_000, do: "#{Float.round(n / 1_000, 1)}k"
   defp format_number(n), do: to_string(n)