feat(plot): PSETUPIN and page-setup import, page setup for new layouts

- PSETUPIN / -PSETUPIN: with no arguments a file picker offers the chosen
  drawing's named page setups in the Plot dialog; `PSETUPIN <file>` opens
  the same chooser on that file; `PSETUPIN <file> *` or
  `PSETUPIN <file> name,name` import straight away. Same-named setups are
  replaced, the import is one undo step, and the report counts both.
- The Plot dialog's page-setup list gains "Import…": the chooser shows the
  source drawing's setups with a tick each, All, Import and Cancel, and
  selects the first imported setup afterwards. The source is read off the
  UI thread with the same reader the editor uses for its own setups
  (`scene::document_page_setups`), and handles that only meant something
  in the source drawing (plot view, visual style) are dropped on import.
- Options → General → Plotting: "Show the page setup for new layouts"
  opens the Plot / Page Setup dialog whenever a layout is created
  (persisted with the plot preferences).

Tests: the document reader, the command (all / named / unknown / missing
file / undo) against a drawing saved by the app, the chooser flow, and the
new-layout option. Nine new strings in all 21 locales.

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

src/ui/window/options.rs

@@ -77,6 +77,8 @@ pub struct AppPrefs {
     pub right_click_mode: RightClickMode,
     /// SHORTCUTMENUDURATION: time-sensitive hold threshold, ms.
     pub right_click_hold_ms: i32,
+    /// Open the Plot / Page Setup dialog for every new layout.
+    pub page_setup_on_new_layout: bool,
 }
 
 /// The fixed locations the Files page lists.
@@ -323,6 +325,29 @@ pub fn view_window<'a>(
         ]
         .spacing(10)
         .align_y(iced::Center),
+        Space::new().height(22),
+        text(crate::t!("Plotting")).size(15),
+        Space::new().height(10),
+        row![
+            text(crate::t!("Plot device, paper, scale and plot styles"))
+                .size(12)
+                .width(Fill),
+            button(text(crate::t!("Plot and Page Setup…")).size(11))
+                .on_press(Message::PlotDialogOpen)
+                .padding([4, 10])
+                .style(button::secondary),
+        ]
+        .spacing(10)
+        .align_y(iced::Center),
+        Space::new().height(10),
+        row![
+            iced::widget::checkbox(prefs.page_setup_on_new_layout)
+                .on_toggle(Message::PageSetupOnNewLayoutChanged)
+                .size(15),
+            text(crate::t!("Show the page setup for new layouts")).size(12),
+        ]
+        .spacing(8)
+        .align_y(iced::Center),
     ]
     .spacing(0)
     .width(sizing.width);
@@ -418,20 +443,6 @@ pub fn view_window<'a>(
         ]
         .spacing(8)
         .align_y(iced::Center),
-        Space::new().height(22),
-        text(crate::t!("Plotting")).size(15),
-        Space::new().height(10),
-        row![
-            text(crate::t!("Plot device, paper, scale and plot styles"))
-                .size(12)
-                .width(Fill),
-            button(text(crate::t!("Plot and Page Setup…")).size(11))
-                .on_press(Message::PlotDialogOpen)
-                .padding([4, 10])
-                .style(button::secondary),
-        ]
-        .spacing(10)
-        .align_y(iced::Center),
     ]
     .spacing(0)
     .width(sizing.width);