Add API v2 output for Latest Batch homepage section

apps/block_scout_web/lib/block_scout_web/api_router.ex

@@ -186,6 +186,7 @@ defmodule BlockScoutWeb.ApiRouter do
       get("/transactions/watchlist", V2.MainPageController, :watchlist_transactions)
       get("/indexing-status", V2.MainPageController, :indexing_status)
       get("/zkevm-confirmed-batches", V2.ZkevmController, :batches_confirmed)
+      get("/zkevm-latest-batch-number", V2.ZkevmController, :batch_latest_number)
     end
 
     scope "/stats" do

apps/block_scout_web/lib/block_scout_web/controllers/api/v2/zkevm_controller.ex

@@ -36,6 +36,18 @@ defmodule BlockScoutWeb.API.V2.ZkevmController do
     |> render(:zkevm_batch, %{batch: batch})
   end
 
+  def batch_latest_number(conn, _params) do
+    number =
+      case Chain.zkevm_batch(:latest, api?: true) do
+        {:ok, batch} -> batch.number
+        {:error, :not_found} -> 0
+      end
+
+    conn
+    |> put_status(200)
+    |> render(:zkevm_batch_latest_number, %{number: number})
+  end
+
   def batches(conn, params) do
     {batches, next_page} =
       params

apps/block_scout_web/lib/block_scout_web/views/api/v2/zkevm_view.ex

@@ -48,6 +48,10 @@ defmodule BlockScoutWeb.API.V2.ZkevmView do
     count
   end
 
+  def render("zkevm_batch_latest_number.json", %{number: number}) do
+    number
+  end
+
   defp batch_status(batch) do
     sequence_id = Map.get(batch, :sequence_id)
     verify_id = Map.get(batch, :verify_id)

apps/explorer/lib/explorer/chain.ex

@@ -6391,7 +6391,20 @@ defmodule Explorer.Chain do
       }
     )
 
-  def zkevm_batch(number, options \\ []) when is_list(options) do
+  def zkevm_batch(number, options \\ [])
+
+  def zkevm_batch(:latest, options) when is_list(options) do
+    ZkevmTxnBatch
+    |> order_by(desc: :number)
+    |> limit(1)
+    |> select_repo(options).one()
+    |> case do
+      nil -> {:error, :not_found}
+      batch -> {:ok, batch}
+    end
+  end
+
+  def zkevm_batch(number, options) when is_list(options) do
     necessity_by_association = Keyword.get(options, :necessity_by_association, %{})
 
     ZkevmTxnBatch