add dashboard filtering to analytics

Click any row in pages, sources, countries, or devices tables to
filter the entire dashboard by that dimension. Active filters show
as dismissible chips. Filters thread through all queries including
previous-period deltas. 1050 tests.

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

test/berrypod_web/live/admin/analytics_test.exs

@@ -102,5 +102,63 @@ defmodule BerrypodWeb.Admin.AnalyticsTest do
       html = render_click(view, "change_tab", %{"tab" => "funnel"})
       assert html =~ "Conversion funnel"
     end
+
+    test "clicking a source adds a filter chip", %{conn: conn} do
+      now = DateTime.utc_now() |> DateTime.truncate(:second)
+
+      Repo.insert_all(Event, [
+        [
+          id: Ecto.UUID.generate(),
+          name: "pageview",
+          pathname: "/",
+          visitor_hash: :crypto.strong_rand_bytes(8),
+          session_hash: :crypto.strong_rand_bytes(8),
+          referrer_source: "Google",
+          inserted_at: now
+        ]
+      ])
+
+      {:ok, view, _html} = live(conn, ~p"/admin/analytics")
+
+      # Switch to sources tab and click the source
+      render_click(view, "change_tab", %{"tab" => "sources"})
+
+      html =
+        render_click(view, "add_filter", %{"dimension" => "referrer_source", "value" => "Google"})
+
+      assert html =~ "Source: Google"
+      assert has_element?(view, "#analytics-filters")
+    end
+
+    test "removing a filter chip clears it", %{conn: conn} do
+      {:ok, view, _html} = live(conn, ~p"/admin/analytics")
+
+      render_click(view, "add_filter", %{"dimension" => "country_code", "value" => "GB"})
+      assert render(view) =~ "Country: United Kingdom"
+
+      html = render_click(view, "remove_filter", %{"dimension" => "country_code"})
+      refute html =~ "Country: United Kingdom"
+    end
+
+    test "clear all removes all filters", %{conn: conn} do
+      {:ok, view, _html} = live(conn, ~p"/admin/analytics")
+
+      render_click(view, "add_filter", %{"dimension" => "country_code", "value" => "GB"})
+      render_click(view, "add_filter", %{"dimension" => "browser", "value" => "Chrome"})
+      assert render(view) =~ "Clear all"
+
+      html = render_click(view, "clear_filters", %{})
+      refute html =~ "Country: United Kingdom"
+      refute html =~ "Browser: Chrome"
+    end
+
+    test "changing period preserves filters", %{conn: conn} do
+      {:ok, view, _html} = live(conn, ~p"/admin/analytics")
+
+      render_click(view, "add_filter", %{"dimension" => "country_code", "value" => "GB"})
+      html = render_click(view, "change_period", %{"period" => "7d"})
+
+      assert html =~ "Country: United Kingdom"
+    end
   end
 end