Feature/endgame play (#1)

* create endgame play section

* add cache tests

* normalise FENs - trim and fuill move to 1 on addition

* remove svg on root and allow navbar to exist across all pages

* update nav items

test/support/fixtures/endgame_fixtures.ex

@@ -0,0 +1,44 @@
+defmodule Chesstrainer.EndgamesFixtures do
+  @moduledoc """
+  This module defines test helpers for creating
+  entities via the `Chesstrainer.Endgames` context.
+  """
+
+  @doc """
+  Generate a unique endgame FEN.
+
+  Endgames have a unique constraint on :fen, so tests need
+  distinct FENs when inserting more than one. Each call
+  shifts the white king's file to avoid FEN collisions.
+  """
+  def unique_endgame_fen do
+    # White king on rank 1 in columns b..g, leaving 1-6 empty squares
+    # before and 6-1 after. Both before_king and after_king are valid
+    # single digits (1-8), and the rank sums to 8.
+    offset = System.unique_integer([:positive]) |> rem(6)
+    before_king = offset + 1
+    after_king = 7 - before_king
+    "4k3/8/8/8/8/8/8/#{before_king}K#{after_king} w - - 0 1"
+  end
+
+  @doc """
+  Generate an endgame.
+
+  A simple K v K position with a unique FEN, color,
+  key, rating, and result.
+  """
+  def endgame_fixture(attrs \\ %{}) do
+    {:ok, endgame} =
+      attrs
+      |> Enum.into(%{
+        fen: unique_endgame_fen(),
+        key: "KQ v K",
+        color: :white,
+        result: :win,
+        rating: 1500
+      })
+      |> Chesstrainer.Endgames.create_endgame()
+
+    endgame
+  end
+end