Feat 为画廊模式添加每页显示图片数量的配置 (#82)

* Feat: Add dynamic image-per-page configuration for gallery mode

- Implemented a slider to configure the number of images displayed per page (1-5) in gallery mode.
- Updated the reader to dynamically reflect changes in the `imagesPerPage` setting without requiring a mode switch or reopening.
- Ensured compatibility with existing continuous reading mode.

* fix currentImagesPerPage

* fix Continuous mode

* improve readerScreenPicNumber setting disable view

* improve PhotoViewController

lib/pages/settings/reader.dart

@@ -41,6 +41,11 @@ class _ReaderSettingsState extends State<ReaderSettings> {
             "continuousTopToBottom": "Continuous (Top to Bottom)".tl,
           },
           onChanged: () {
+            var readerMode = appdata.settings['readerMode'];
+            if (readerMode?.toLowerCase().startsWith('continuous') ?? false) {
+              appdata.settings['readerScreenPicNumber'] = 1;
+              widget.onChanged?.call('readerScreenPicNumber');
+            }
             widget.onChanged?.call("readerMode");
           },
         ).toSliver(),
@@ -54,6 +59,25 @@ class _ReaderSettingsState extends State<ReaderSettings> {
             widget.onChanged?.call("autoPageTurningInterval");
           },
         ).toSliver(),
+        SliverToBoxAdapter(
+          child: AbsorbPointer(
+            absorbing: (appdata.settings['readerMode']?.toLowerCase().startsWith('continuous') ?? false),
+            child: AnimatedOpacity(
+              opacity: (appdata.settings['readerMode']?.toLowerCase().startsWith('continuous') ?? false) ? 0.5 : 1.0,
+              duration: Duration(milliseconds: 300),
+              child: _SliderSetting(
+                title: "The number of pic in screen (Only Gallery Mode)".tl,
+                settingsIndex: "readerScreenPicNumber",
+                interval: 1,
+                min: 1,
+                max: 5,
+                onChanged: () {
+                  widget.onChanged?.call("readerScreenPicNumber");
+                },
+              ),
+            ),
+          ),
+        ),
         _SwitchSetting(
           title: 'Long press to zoom'.tl,
           settingKey: 'enableLongPressToZoom',