feat(settings): migrate Export All Keys modal to the reference design

Phase 1. DialogWarningHeader care header (was a hand-rolled red icon+text);
centered DialogActionFooter (Export + Close) replacing the StyledButtons + two
separators; on full success the saved path shows in a copy field with a green
check, partial/error render inline; export progress uses LoadingDots. Full i18n:
the previously-hardcoded notification + status strings now use TR (8 new
export_keys_* keys in en + 8 langs). Added hide() + a modal-export-all-keys sweep
surface. Also fixes a latent Begin/EndOverlayDialog imbalance on the 0-address
early return. No change to the export RPC logic.

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

res/lang/zh.json

@@ -373,10 +373,18 @@
     "export_keys_danger": "危险：这将导出您钱包中的所有私钥！任何获得此文件的人都可以窃取您的资金。请安全保管并在使用后删除。",
     "export_keys_include_t": "包含 T 地址（透明）",
     "export_keys_include_z": "包含 Z 地址（屏蔽）",
+    "export_keys_none_addrs": "没有可导出的地址",
+    "export_keys_none_result": "未导出任何密钥（%d 个中 0 个）——请解锁钱包后重试。",
+    "export_keys_none_toast": "无法导出密钥——钱包已解锁吗？",
+    "export_keys_not_connected": "未连接到守护进程",
     "export_keys_options": "导出选项：",
+    "export_keys_partial": "已导出 %d/%d 个密钥——不完整（部分没有花费密钥，或钱包已锁定）。",
+    "export_keys_partial_toast": "部分导出：%d/%d 个密钥",
     "export_keys_progress": "正在导出 %d/%d...",
+    "export_keys_select_type": "请至少选择一种地址类型",
     "export_keys_success": "密钥导出成功",
     "export_keys_title": "导出所有私钥",
+    "export_keys_write_fail": "写入密钥文件失败。",
     "export_private_key": "导出私钥",
     "export_tx_count": "导出 %zu 笔交易到 CSV 文件。",
     "export_tx_file_fail": "无法创建 CSV 文件",