side rail initial

apps/weblibre/lib/features/user/data/models/general_settings.dart

@@ -87,7 +87,23 @@ enum TabIntentOpenSetting { regular, private, isolated, ask }
 
 enum TabDirection { newestFirst, oldestFirst }
 
-enum TabBarPosition { top, bottom }
+enum TabBarPosition {
+  top,
+  bottom,
+  left,
+  right;
+
+  /// Whether the tab bar is rendered as a vertical side rail (left/right)
+  /// rather than a horizontal bar (top/bottom).
+  bool get isVertical =>
+      this == TabBarPosition.left || this == TabBarPosition.right;
+
+  /// Whether the tab bar is rendered as a horizontal bar (top/bottom).
+  bool get isHorizontal => !isVertical;
+
+  /// Main axis along which the bar's content flows.
+  Axis get axis => isVertical ? Axis.vertical : Axis.horizontal;
+}
 
 enum TabBarLayout { withTitle, compact }
 

apps/weblibre/lib/features/user/data/models/general_settings.g.dart

@@ -1246,6 +1246,8 @@ const _$TabBarSwipeActionEnumMap = {
 const _$TabBarPositionEnumMap = {
   TabBarPosition.top: 'top',
   TabBarPosition.bottom: 'bottom',
+  TabBarPosition.left: 'left',
+  TabBarPosition.right: 'right',
 };
 
 const _$TabBarLayoutEnumMap = {