add entry/exit pages panel to analytics dashboard

ROW_NUMBER() window function picks first/last pageview per session.
Both tables live in the pages tab and support the pathname filter.
6 new tests, 1061 total.

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

test/berrypod/analytics_test.exs

@@ -287,6 +287,85 @@ defmodule Berrypod.AnalyticsTest do
     end
   end
 
+  describe "entry_pages/2" do
+    test "returns the first page per session" do
+      s1 = :crypto.strong_rand_bytes(8)
+      s2 = :crypto.strong_rand_bytes(8)
+      now = DateTime.utc_now() |> DateTime.truncate(:second)
+      earlier = DateTime.add(now, -60, :second)
+
+      insert_event(%{session_hash: s1, pathname: "/", inserted_at: earlier})
+      insert_event(%{session_hash: s1, pathname: "/about", inserted_at: now})
+      insert_event(%{session_hash: s2, pathname: "/products", inserted_at: earlier})
+
+      pages = Analytics.entry_pages(today_range())
+      pathnames = Enum.map(pages, & &1.pathname)
+
+      assert "/" in pathnames
+      assert "/products" in pathnames
+      refute "/about" in pathnames
+    end
+
+    test "counts sessions per entry page" do
+      s1 = :crypto.strong_rand_bytes(8)
+      s2 = :crypto.strong_rand_bytes(8)
+      s3 = :crypto.strong_rand_bytes(8)
+      now = DateTime.utc_now() |> DateTime.truncate(:second)
+
+      insert_event(%{session_hash: s1, pathname: "/"})
+      insert_event(%{session_hash: s2, pathname: "/"})
+      insert_event(%{session_hash: s3, pathname: "/about", inserted_at: now})
+
+      pages = Analytics.entry_pages(today_range())
+      home = Enum.find(pages, &(&1.pathname == "/"))
+      assert home.sessions == 2
+    end
+
+    test "returns empty list with no data" do
+      assert Analytics.entry_pages(today_range()) == []
+    end
+  end
+
+  describe "exit_pages/2" do
+    test "returns the last page per session" do
+      s1 = :crypto.strong_rand_bytes(8)
+      s2 = :crypto.strong_rand_bytes(8)
+      now = DateTime.utc_now() |> DateTime.truncate(:second)
+      earlier = DateTime.add(now, -60, :second)
+
+      insert_event(%{session_hash: s1, pathname: "/", inserted_at: earlier})
+      insert_event(%{session_hash: s1, pathname: "/about", inserted_at: now})
+      insert_event(%{session_hash: s2, pathname: "/products", inserted_at: earlier})
+
+      pages = Analytics.exit_pages(today_range())
+      pathnames = Enum.map(pages, & &1.pathname)
+
+      assert "/about" in pathnames
+      assert "/products" in pathnames
+      refute "/" in pathnames
+    end
+
+    test "counts sessions per exit page" do
+      s1 = :crypto.strong_rand_bytes(8)
+      s2 = :crypto.strong_rand_bytes(8)
+      now = DateTime.utc_now() |> DateTime.truncate(:second)
+      earlier = DateTime.add(now, -60, :second)
+
+      insert_event(%{session_hash: s1, pathname: "/", inserted_at: earlier})
+      insert_event(%{session_hash: s1, pathname: "/about", inserted_at: now})
+      insert_event(%{session_hash: s2, pathname: "/", inserted_at: earlier})
+      insert_event(%{session_hash: s2, pathname: "/about", inserted_at: now})
+
+      pages = Analytics.exit_pages(today_range())
+      about = Enum.find(pages, &(&1.pathname == "/about"))
+      assert about.sessions == 2
+    end
+
+    test "returns empty list with no data" do
+      assert Analytics.exit_pages(today_range()) == []
+    end
+  end
+
   describe "delete_events_before/1" do
     test "deletes old events" do
       old = DateTime.add(DateTime.utc_now(), -400, :day) |> DateTime.truncate(:second)