feat: add monthly budget field and statistics (#329)

includes/i18n/jp.php

@@ -85,7 +85,11 @@ $i18n = [
     'average_monthly' => "月額平均費用",
     'most_expensive'  => "最も高額な定期購入費用",
     'amount_due'      => "今月の支払額",
+    'percentage_budget_used' => "予算使用率",
+    'budget_remaining' => "予算残高",
+    'amount_over_budget' => "予算オーバー",
     'monthly_savings' => "月間節約 (非アクティブな定期購入)",
+    'yearly_savings'  => "年間節約 (非アクティブな定期購入)",
     'split_views'     => "分割表示",
     'category_split'  => "カテゴリ別",
     'household_split' => "世帯別",
@@ -101,7 +105,9 @@ $i18n = [
     'upload_avatar'   => "アバターをアップロードする",
     'file_type_error' => "ファイルタイプが許可されていません",
     'user_details'    => "ユーザー詳細",
-    "household"        => "世帯",
+    "monthly_budget"  => "月間予算",
+    "budget_info"     => "予算を設定すると、統計ページで予算と実際の支出を比較できます。",
+    "household"       => "世帯",
     "save_member"     => "世帯員を保存",
     "delete_member"   => "世帯員を削除",
     "cant_delete_member" => "世帯主は削除出ません",