feat(console): persist accent toggle + add monochrome-text toggle

Persist the two console output display preferences and add a second toolbar
toggle for monochrome text.

- Persistence: new Settings fields console_line_accents / console_text_color
  (both default true, matching the ConsoleTab statics so an upgrade re-save
  can't flip visible behavior). Restored into the statics at startup in the App
  constructor, and saved from a diff-and-save after the console renders (only
  when a value actually changed — save() is disk I/O). The startup restore also
  fixes a pre-existing bug: scanline was only synced from settings when the
  Settings page or first-run wizard ran, so an existing wallet ignored a saved
  scanline preference on launch.
- Monochrome text: a new toolbar toggle (FORMAT_COLOR_TEXT, dimmed when off)
  next to the accent toggle. channelTextColor() early-returns the neutral
  COLOR_RESULT for every channel (and JSON syntax role) when off, leaving the
  left accent bars independent. COLOR_RESULT is contrast-floored per theme, so
  text stays readable on light and dark terminals.

Adds console_toggle_text_color to the English source + all 8 translations.
Verified: both toggles independent, persistence round-trips across restart,
monochrome readable on light + dark skins.

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

res/lang/ko.json

@@ -241,6 +241,7 @@
     "console_status_unknown": "알 수 없음",
     "console_tab_completion": "Tab으로 자동 완성",
     "console_toggle_accents": "줄 색상 강조 전환",
+    "console_toggle_text_color": "줄 텍스트 색상 전환",
     "console_type_help": "'help'를 입력하여 사용 가능한 명령어 보기",
     "console_welcome": "ObsidianDragon 콘솔에 오신 것을 환영합니다",
     "console_zoom_in": "확대",