feat(wallets): fixed max-height list + manage scanned folders

Two wallets-modal changes:

- The wallet list now always renders at its max height (kMaxVisibleRows) instead
  of shrinking to the wallet count, so the modal is a consistent size whether you
  have one wallet or many — fewer rows leave empty space, more than 7 scroll.

- Add a "Scanned folders" manager: each user-added scan folder is listed with a
  control to stop scanning it (removeExtraFolder + save + re-scan so its wallets
  drop out). Paths front-elide to keep the identifying leaf visible, with a
  full-path tooltip. The card-height math reserves the manager's rows so nothing
  clips. Two new i18n keys (wallets_scanned_folders / wallets_remove_folder),
  translated across all 8 languages; CJK subset rebuilt.

Verified on the sweep at 1.0 and 1.5x DPI: max-height list on both the few- and
many-wallet surfaces, the folder manager renders and stays clear of the footer.

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

res/lang/ja.json

@@ -1356,7 +1356,9 @@
     "wallets_open_failed": "このウォレットをその場で開けませんでした。データディレクトリとは別のドライブにある可能性があります — 同じドライブに移動してください（Windows では開発者モードを有効にするとドライブ間のリンクも可能になります）。",
     "wallets_open_folder": "フォルダーの場所を開く",
     "wallets_open_inplace_tt": "このウォレットをその場で開きます — データディレクトリにリンク（コピーなし）",
+    "wallets_remove_folder": "このフォルダーのスキャンを停止",
     "wallets_reveal": "フォルダを開く",
+    "wallets_scanned_folders": "スキャン対象フォルダー：",
     "wallets_sort_addresses": "アドレス",
     "wallets_sort_asc": "昇順（古い/少ない/小さい順）",
     "wallets_sort_by": "並べ替え：",