feat(migrate): daemon-update prompt + migrate-to-seed UX polish + i18n

Fixes the Windows migrate-to-seed failure (the old bundled daemon lacked
z_exportmnemonic) and rounds out the flow:

- seed_wallet_creator: actionable "daemon too old" message instead of the
  raw "Method not found" RPC error.
- Startup daemon-update prompt: if the wallet bundles a newer node than the
  installed one, offer to update it (once per version, keyed on a new
  daemon_update_prompted_size setting; never silently clobbers a custom
  node). "Install bundled" now also works when attached to an external /
  leftover daemon (RPC-stops it, then swaps + restarts).
- Migrate-to-seed Intro pre-flight: detect an already-mnemonic wallet
  (offer backup instead), an old daemon, or a locked/disconnected wallet
  before offering to create anything.
- No-funds path: a zero-balance wallet can adopt the new seed wallet
  directly (behind an acknowledgement checkbox) instead of a dead sweep.
- Loading spinners on the Working/Sweeping/Adopting steps; sweep coverage
  for the new intro / no-funds surfaces.
- Translations for all 18 new strings across 8 languages (+ rebuilt CJK
  subset font).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/zh.json

@@ -227,6 +227,11 @@
     "copy_uri": "复制 URI",
     "current_price": "当前价格",
     "custom_fees": "自定义手续费",
+    "daemon_update_body": "此钱包版本内置的 DragonX 节点比当前已安装的更新。更新会替换已安装的 dragonxd（以及 dragonx-cli/dragonx-tx），然后停止并重启节点以使新版本生效。推荐更新——更新的节点可能增加旧版本所缺少的功能（例如助记词支持）。",
+    "daemon_update_keep": "保持当前版本",
+    "daemon_update_now": "立即更新",
+    "daemon_update_safe": "您的钱包、密钥和区块链数据不会被改动——仅替换守护进程的程序文件。如果您是有意运行自定义节点，请选择“保持当前版本”。",
+    "daemon_update_title": "更新节点守护进程？",
     "daemon_version": "守护进程",
     "dark": "深色",
     "date": "日期",
@@ -384,21 +389,33 @@
     "merge_started": "合并操作已开始",
     "merge_title": "合并到地址",
     "mig_adopt": "将其设为我的钱包",
+    "mig_adopt_now": "采用助记词钱包",
     "mig_adopting": "正在安装您的新钱包并重新扫描…",
+    "mig_adopting_note": "节点正在您的新钱包上重启，并将重新扫描区块链——这可能需要几分钟。请让钱包保持运行；它会自动重新连接。",
+    "mig_already_mnemonic": "您的钱包已经有 24 词助记词——无需迁移。只需备份它并将这些词妥善保存在安全的地方即可。",
     "mig_backed_up": "我已抄写下我的助记词",
+    "mig_backup_instead": "备份助记词",
     "mig_balance": "当前钱包余额：%.8f DRGX（扣除少量手续费）",
+    "mig_check_failed": "无法检查您的钱包。请确保它已解锁并已连接，然后重新检查。",
+    "mig_checking_balance": "正在检查您的余额",
     "mig_confirming": "正在等待此次扫入在链上确认，然后再切换钱包——这可确保您的资金确实已经转移。",
     "mig_confs": "扫入确认数：%d",
     "mig_continue_sweep": "继续扫入",
     "mig_copy_seed": "复制助记词",
     "mig_create": "创建助记词钱包",
+    "mig_daemon_too_old": "您的 DragonX 节点版本太旧，无法创建助记词钱包——它缺少此功能所需的助记词支持。请更新节点（设置 → 节点与安全 → 安装内置版本，或检查更新），然后重试。",
     "mig_discard": "放弃迁移",
     "mig_done": "迁移完成。您的钱包现在由您的助记词支持。",
     "mig_done_btn": "完成",
     "mig_done_detail": "守护进程正在重新扫描以显示您的资金——这可能需要几分钟。您之前的钱包已作为 .bak 保存在数据文件夹中。",
     "mig_intro": "这会在一个隔离的节点中创建一个由 24 词助记词支持的全新钱包，以便您将资金转入其中。您当前的钱包不会受到影响，本步骤也不会转移任何资金——您将先备份新助记词，然后再作为单独的、经确认的步骤把资金扫入其中。",
     "mig_later": "稍后",
+    "mig_no_funds": "您的钱包没有可迁移的资金。您可以直接采用新的助记词钱包——它会用由助记词支持的钱包替换您当前的（空）钱包。以防万一，您的旧钱包仍会移到一个带时间戳的备份中。",
+    "mig_nofunds_confirm": "我明白这会用新的助记词钱包替换我当前的钱包",
+    "mig_not_connected": "请先连接到您的节点，然后重新打开此界面进行迁移。",
+    "mig_precheck_checking": "正在检查您的钱包",
     "mig_receive_addr": "新钱包接收地址：",
+    "mig_recheck": "重新检查",
     "mig_remainder": "您的旧钱包中仍有部分资金（一笔交易的输入过多）——请在切换前扫入剩余部分。",
     "mig_remaining": "旧钱包中剩余：%.8f DRGX",
     "mig_seed_warning": "请按顺序将这 24 个词抄写下来并离线保存。它们是您新钱包唯一的备份——一旦丢失，您迁移的资金将永久无法恢复。",
@@ -411,6 +428,7 @@
     "mig_to": "至：",
     "mig_txid": "txid: ",
     "mig_unlock_first": "请先解锁您的钱包才能从中花费。",
+    "mig_unlock_to_migrate": "请先解锁您的钱包，然后重新打开此界面进行迁移。",
     "mig_waiting_mine": "正在等待扫入交易被打包…",
     "mig_working": "正在隔离的节点中创建您的新助记词钱包——这可能需要一分钟。您的主钱包将继续运行。",
     "mine_when_idle": "空闲时挖矿",