Route remaining hardcoded UI strings through the locale system

Main menu buttons, the confirm dialog, battle menu/HUD text, backpack
tab labels, the loading/autosave indicators, and the settings tab
placeholders were all raw English literals bypassing translation.
Loads each through assetLocaleGetString like the rest of the UI, adding
new Init hooks for uibattlehud/uiautosave/uiloading where none existed,
and adds the corresponding message ids to en_US/es_MX/jp_JP.po.

Also widens the settings placeholder buffers to 64 bytes - the es_MX
and jp_JP translations overflowed the previous 32-byte size.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

assets/locale/jp_JP.po

@@ -113,6 +113,74 @@ msgstr "はい"
 msgid "ui.initial.create_save.no"
 msgstr "いいえ"
 
+#: src/dusk/ui/frame/mainmenu/uimainmenu.c
+msgid "ui.main_menu.new_game"
+msgstr "ニューゲーム"
+
+#: src/dusk/ui/frame/mainmenu/uimainmenu.c
+msgid "ui.main_menu.load_game"
+msgstr "ロードゲーム"
+
+#: src/dusk/ui/frame/mainmenu/uimainmenu.c
+msgid "ui.main_menu.options"
+msgstr "オプション"
+
+#: src/dusk/ui/frame/mainmenu/uimainmenu.c
+msgid "ui.main_menu.quit"
+msgstr "ゲームを終了"
+
+#: src/dusk/ui/frame/uiconfirm.c
+msgid "ui.confirm.confirm"
+msgstr "確認"
+
+#: src/dusk/ui/frame/uiconfirm.c
+msgid "ui.confirm.cancel"
+msgstr "キャンセル"
+
+#: src/dusk/ui/frame/battle/uibattlemenu.c
+msgid "ui.battle.menu.attack"
+msgstr "攻撃"
+
+#: src/dusk/ui/frame/battle/uibattlemenu.c
+msgid "ui.battle.menu.flee"
+msgstr "逃げる"
+
+#: src/dusk/ui/frame/battle/uibattlemenu.c
+msgid "ui.battle.menu.target_format"
+msgstr "敵%u (%u/%u HP)"
+
+#: src/dusk/ui/frame/battle/uibattlehud.c
+msgid "ui.battle.hud.hp_format"
+msgstr "HP %u/%u"
+
+#: src/dusk/ui/frame/battle/uibattlehud.c
+msgid "ui.battle.hud.mp_format"
+msgstr "MP %u/%u"
+
+#: src/dusk/ui/frame/settings/uisettingsaudio.c
+msgid "ui.settings.audio.placeholder"
+msgstr "オーディオ設定はまだありません"
+
+#: src/dusk/ui/frame/settings/uisettingsdisplay.c
+msgid "ui.settings.display.placeholder"
+msgstr "表示設定はまだありません"
+
+#: src/dusk/ui/frame/settings/uisettingsinput.c
+msgid "ui.settings.input.placeholder"
+msgstr "入力設定はまだありません"
+
+#: src/dusk/ui/frame/backpack/uibackpack.c
+msgid "ui.backpack.category_format"
+msgstr "カテゴリー%u"
+
+#: src/dusk/ui/overlay/uiloading.c
+msgid "ui.loading.text"
+msgstr "読み込み中"
+
+#: src/dusk/ui/overlay/uiautosave.c
+msgid "ui.autosave.saving"
+msgstr "保存中"
+
 #: src/dusk/rpg/item/item.json
 msgid "item.potion.name"
 msgstr "ポーション"