perf(net): hold wallet scans at connect, in the background and on tab entry

- Connect gate: after the node starts answering, wallet scans wait until the
  lock state is known and the node knows its tip (or the wallet has fewer
  than 500 transactions), at most 20 s. A node already behind latches the
  sync profile from the connect's getinfo. Meanwhile a list-only pass keeps
  the address list and the cached history up, and the session's first
  balance and per-address balances are read once even while catching up,
  so the wallet shows its last-synced values instead of 0.
- Background: minimized, hidden, or covered without focus (3 s debounce,
  any input cancels) polls only the chain state every 15 s. Wallet scans,
  the mining poll, price, nudges and auto-lock interaction tracking pause;
  auto-lock now fires while minimized. Leaving a held profile marks every
  timer due again.
- Tab entry marks the timers due instead of forcing scans; a stale list or
  a never-loaded history still loads on entry.
- The scan entry points own the hard gates, failed enumerations keep the
  previous lists behind a retry hold, and failed balance calls never
  overwrite known balances with 0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

res/lang/zh.json

@@ -1561,6 +1561,7 @@
     "reduce_motion": "减少动画",
     "refresh": "刷新",
     "refresh_now": "立即刷新",
+    "refresh_waits_for_sync": "节点仍在同步。同步完成后将刷新钱包数据。",
     "remove_favorite": "移除收藏",
     "repair_wallet": "修复钱包",
     "report_bug": "报告错误",
@@ -2127,6 +2128,7 @@
     "tx_loading_queued": "已排队的交易刷新",
     "tx_loading_refreshing_cached": "正在刷新钱包历史（已缓存 %d 条）",
     "tx_loading_scanning_shielded": "正在扫描屏蔽历史（%d 个地址）",
+    "tx_loading_waits_for_sync": "节点同步完成后将更新历史记录",
     "tx_mined": "已挖得",
     "tx_progress_balances": "正在刷新余额",
     "tx_progress_finalizing": "正在完成交易",