feat: CJK font rendering, force quit confirmation, settings i18n

- Rebuild CJK font subset (1421 glyphs) and convert CFF→TTF for
  stb_truetype compatibility, fixing Chinese/Japanese/Korean rendering
- Add force quit confirmation dialog with cancel/confirm actions
- Show force quit tooltip immediately on hover (no delay)
- Translate hardcoded English strings in settings dropdowns
  (auto-lock timeouts, slider "Off" labels)
- Fix mojibake en-dashes in 7 translation JSON files
- Add helper scripts: build_cjk_subset, convert_cjk_to_ttf,
  check_font_coverage, fix_mojibake

res/lang/zh.json

@@ -652,7 +652,7 @@
     "show": "显示",
     "show_hidden": "显示已隐藏 (%d)",
     "show_qr_code": "显示二维码",
-    "showing_transactions": "显示第 %d–%d 笔，共 %d 笔交易（总计：%zu）",
+    "showing_transactions": "显示第 %d–%d 笔，共 %d 笔交易（总计：%zu）",
     "simple_background": "简单背景",
     "start_mining": "开始挖矿",
     "status": "状态",