移除日历视图：功能与决策卡重叠，维护成本高于价值

- 删除 CalendarView.tsx、calendar-action-utils.ts 及其测试文件
- 删除 ScanTerminalCalendar.module.css
- ScanTerminalDashboard：移除日历 tab 按钮、日历渲染分支、ContentView 类型中的 calendar
- ScanTerminalLightTheme：清理所有 .scan-calendar-* 规则（~40 行）
- scan-root-styles.ts：移除 ScanTerminalCalendar 导入

同时完善地理排序：
- scan_terminal_filters.py：market_region_from_tz_offset 细化为 7 个区域（东亚/东南亚/中亚/西亚/欧洲非洲/南美/北美）并增加 sort_order
- scan_terminal_city_row.py：传递 trading_region_sort
- dashboard-types.ts：增加 trading_region_sort 字段
- decision-utils.ts：sortRowsByUserTime 按 trading_region_sort 优先排序

Rejected: keep-calendar-view, calendar-actions-overlap-with-decision-cards
Tested: npx tsc --noEmit, python -m ruff check .

frontend/components/dashboard/scan-root-styles.ts

@@ -16,7 +16,6 @@ import historyModalStyles from "./HistoryModal.module.css";
 import modalChromeStyles from "./ModalChrome.module.css";
 import scanTerminalStyles from "./ScanTerminal.module.css";
 import scanTerminalBoardStyles from "./ScanTerminalBoard.module.css";
-import scanTerminalCalendarStyles from "./ScanTerminalCalendar.module.css";
 import scanTerminalCardStyles from "./ScanTerminalCard.module.css";
 import scanTerminalDetailStyles from "./ScanTerminalDetail.module.css";
 import scanTerminalFiltersStyles from "./ScanTerminalFilters.module.css";
@@ -41,7 +40,6 @@ export const scanRootClass = clsx(
   scanTerminalStateStyles.root,
   scanTerminalOpportunityStyles.root,
   scanTerminalCardStyles.root,
-  scanTerminalCalendarStyles.root,
   scanTerminalMobileStyles.root,
   scanTerminalLightThemeStyles.root,
   detailChromeStyles.root,