feat(start): recent files as a list, icons or large previews

Three toggles beside the Recent Documents title switch the panel between
the existing list, a grid of thumbnail tiles and one large preview per
file. The choice is kept in the recent section of the app config.

Refs #1494

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/update/file.rs

@@ -1326,6 +1326,7 @@ impl OpenCADStudio {
                     .map(|p| p.to_string_lossy().into_owned())
                     .collect(),
                 limit: self.recent_limit,
+                view: self.recent_view,
             },
             start: crate::app::config::StartConfig {
                 section: self.start_section,
@@ -1397,6 +1398,7 @@ impl OpenCADStudio {
         );
         self.recent_files.truncate(self.recent_limit);
         self.recent_limit_input = self.recent_limit.to_string();
+        self.recent_view = cfg.recent.view;
         // Thumbnails are decoded by a background task queued at boot
         // (`refresh_recent_thumbs`) — never here on the boot path.
         self.start_section = cfg.start.section;

src/app/update/mod.rs

@@ -1153,6 +1153,12 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::SetRecentView(view) => {
+                self.recent_view = view;
+                self.save_config();
+                Task::none()
+            }
+
             Message::RecentLimitInput(s) => {
                 // Keep only digits while typing; applied on Enter (SetRecentLimit).
                 self.recent_limit_input = s.chars().filter(|c| c.is_ascii_digit()).collect();