feat(mining): thread-count stepper, adaptive tiles, dropdown click-through fix, xmrig version state

Mining-tab UI improvements:
- Thread selector: a centered [-] N [+] stepper (top-aligned in the header) to pick an exact
  thread count — number centered, -/+ step by one (clamped to [1, cores]), still typeable
  (commits on Enter so it doesn't restart the miner mid-typing).
- Thread tiles now render at an adaptive step (1/2/4/8 by core count) plus 1 and the max, so a
  high-core CPU (e.g. a 192-thread EPYC) shows ~25 tiles instead of one-per-thread and no longer
  overflows the card. Unchanged for <=24-core machines.
- Fix: clicking the X (or a row) in an open saved-pools / payout-address dropdown no longer bleeds
  through to the thread tiles / Mine button — the custom drawlist hit-tests now gate on
  IsPopupOpen(AnyPopup).
- xmrig update button: shows "xmrig releases" when installed >= latest (numeric version compare),
  else "Update <latest>"; the "Current: <ver>" text and the button are subtle green when up to date
  and subtle orange when an update is available (neutral when either version is unknown).

New i18n keys back-filled across all 8 languages; CJK subset font rebuilt for the new glyphs.
Verified across full-node, lite, and Windows builds; the stepper layout confirmed via the UI sweep.

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

res/lang/ja.json

@@ -949,6 +949,9 @@
     "mining_syncing_tooltip": "ブロックチェーン同期中...",
     "mining_tag": " · マイニング",
     "mining_threads": "マイニングスレッド",
+    "mining_threads_input_tooltip": "正確なスレッド数を入力（Enter で適用）",
+    "mining_threads_minus_tooltip": "スレッドを減らす",
+    "mining_threads_plus_tooltip": "スレッドを増やす",
     "mining_to_save": "保存する",
     "mining_today": "今日",
     "mining_uptime": "稼働時間",
@@ -1782,6 +1785,7 @@
     "xmrig_loading_releases": "リリースを読み込み中…",
     "xmrig_none": "なし",
     "xmrig_reinstall": "再インストール",
+    "xmrig_releases": "xmrig リリース",
     "xmrig_stop_mining_first": "マイナーを更新する前にマイニングを停止してください。",
     "xmrig_unavailable_body": "このプラットフォーム向けのマイナービルドは利用できません。",
     "xmrig_unavailable_title": "マイナーの更新は利用できません",