feat: wire App with reading view dispatch, theme toggle, and reading position save

src/app.rs

@@ -143,6 +143,44 @@ impl eframe::App for App {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         if self.state.book.is_none() {
             self.welcome_view(ctx);
+            return;
         }
+
+        let file_path = self.state.file_path
+            .as_ref()
+            .map(|p| p.to_string_lossy().to_string())
+            .unwrap_or_default();
+
+        egui::CentralPanel::default().show(ctx, |ui| {
+            let book = self.state.book.as_mut().unwrap();
+            let action = crate::reader::reading_view(
+                ui,
+                book,
+                &mut self.state.current_section,
+                &mut self.state.current_page,
+                &mut self.state.sidebar_open,
+                &mut self.settings.font_size,
+                &self.settings.theme,
+                &file_path,
+            );
+
+            if action.go_back {
+                self.save_reading_position();
+                self.state.book = None;
+                self.state.current_section = 0;
+                self.state.current_page = 0;
+            }
+
+            if action.toggle_theme {
+                self.settings.theme = match self.settings.theme {
+                    theme::Theme::Light => theme::Theme::Dark,
+                    theme::Theme::Dark => theme::Theme::Light,
+                };
+                ctx.set_style(theme::create_style(&self.settings.theme));
+            }
+        });
+
+        self.save_reading_position();
+        self.save_settings();
     }
 }