feat(ui): Add menu bar and customizable quick toolbar (v0.7.0)

- Menu bar groups all functions: File (import/MRU/exports), View
  (zoom/standard views/ortho/unit), Measure (7 checkable modes with
  hotkey hints), Transform (align/drag/gizmo/rotate), Tools
  (interference/section), QuickBar (customize/reset)
- QuickBarViewModel registry: per-button visibility via XAML indexer
  binding QuickBar[Key].IsChecked; buttons keep static bindings
- Common-user defaults visible (import/recent/zoom/iso/ortho/point/
  distance/circle/angle/interference/section/clear/unit); the rest
  live in menus; selection persists in settings.json QuickBarKeys
- Section parameter bar is its own row, shown only while section is
  enabled (with close button); no longer occupies space permanently
- Bump version to 0.7.0; update ARCHITECTURE/CLAUDE docs (Phase 16)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -47,6 +47,10 @@ dotnet publish src/STPViewer -c Release -o publish/STPViewer
   （量孔對孔 pitch 靠這個）。不要把圓心吸附拿掉或改成永遠優先頂點
 - 鍵盤快速鍵在 `MainWindow.Window_PreviewKeyDown`：**焦點在 TextBoxBase/ComboBox 時直接 return**
   （樹搜尋框、剖面數值框要能打字），新增輸入控件不用再各自處理
+- UI 三層（v0.7.0）：**選單列**（全部功能，分類下拉）+ **快速列**（`QuickBarViewModel` 註冊表，
+  使用者勾選常用按鈕，XAML 索引子綁定 `QuickBar[Key].IsChecked` 控 Visibility，按鈕本體維持靜態綁定）+
+  **剖面參數列**（只在 SectionEnabled 顯示）。新增功能要三處都接：選單分類、快速列註冊表
+  （含預設值）+ 對應 XAML 按鈕；勾選清單存 settings.json `QuickBarKeys`（null = 預設）
 - 使用者設定 `SettingsService`（%LOCALAPPDATA%\STPViewer\settings.json）：視窗（MainWindow 管）+
   單位/MRU（VM `LoadSettings`/`SaveSettingsInto`）；壞檔回預設、儲存失敗靜默
 - 匯出 STEP 走 `CADability.ExportStep.WriteToFile(file, Project.CreateSimpleProject()+Model.Add)`；