Add a Settings option to reorder the selection action bar's actions

NooSelectionBar's fixed inline slots (3 mobile / 4 desktop, the rest
behind "More") previously just took the first N actions in whatever
order each screen happened to build them in. Give bulk actions a
stable SelectionActionKind identity (independent of their dynamic
icon/label, e.g. favorite vs. unfavorite) so Settings can offer a
drag-to-reorder list - mirroring the existing Tabs section, minus the
pin/hide concept, which doesn't apply here - and each screen applies
that saved priority order via orderSelectionActions before handing
its action list to the bar.

lib/providers/settings_controller.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import '../models/app_tab.dart';
+import '../models/selection_action.dart';
 import '../theme/app_theme.dart';
 
 /// What swiping a Files list-view item left/right does, user-configurable
@@ -24,6 +25,7 @@ class SettingsController extends ChangeNotifier {
   static const _prefUseDynamicColor = 'ui_use_dynamic_color';
   static const _prefSeedColor = 'ui_seed_color';
   static const _prefTabOrder = 'ui_tab_order';
+  static const _prefSelectionActionOrder = 'ui_selection_action_order';
   static const _prefHiddenTabs = 'ui_hidden_tabs';
   static const _prefDefaultTab = 'ui_default_tab';
   static const _prefSwipeLeftAction = 'ui_swipe_left_action';
@@ -47,6 +49,9 @@ class SettingsController extends ChangeNotifier {
   Set<AppTab> _hiddenTabs = {};
   AppTab _defaultTab = AppTab.files;
 
+  List<SelectionActionKind> _selectionActionOrder = SelectionActionKind.values
+      .toList();
+
   SwipeAction _swipeLeftAction = SwipeAction.delete;
   SwipeAction _swipeRightAction = SwipeAction.favorite;
 
@@ -86,6 +91,12 @@ class SettingsController extends ChangeNotifier {
   Set<AppTab> get hiddenTabs => _hiddenTabs;
   AppTab get defaultTab => _defaultTab;
 
+  /// The priority order bulk actions (favorite, share, download, ...) show
+  /// in on the multi-select action bar - see [orderSelectionActions]. Every
+  /// [SelectionActionKind] is always present here (nothing is hidden, only
+  /// reordered), so [NooSelectionBar]'s fixed inline slots are always full.
+  List<SelectionActionKind> get selectionActionOrder => _selectionActionOrder;
+
   /// The tabs the bottom nav bar should actually show, in order.
   List<AppTab> get visibleTabs =>
       _tabOrder.where((t) => !_hiddenTabs.contains(t)).toList();
@@ -134,6 +145,25 @@ class SettingsController extends ChangeNotifier {
         _tabOrder = order;
       }
 
+      final savedActionOrderNames = prefs.getStringList(
+        _prefSelectionActionOrder,
+      );
+      if (savedActionOrderNames != null) {
+        final order = <SelectionActionKind>[];
+        for (final name in savedActionOrderNames) {
+          final match = SelectionActionKind.values
+              .where((k) => k.name == name)
+              .firstOrNull;
+          if (match != null) order.add(match);
+        }
+        // Forward-compat: a kind added in a later app update won't be in an
+        // older saved order yet, so append anything missing.
+        for (final kind in SelectionActionKind.values) {
+          if (!order.contains(kind)) order.add(kind);
+        }
+        _selectionActionOrder = order;
+      }
+
       final savedHiddenNames = prefs.getStringList(_prefHiddenTabs);
       if (savedHiddenNames != null) {
         _hiddenTabs = savedHiddenNames
@@ -234,6 +264,17 @@ class SettingsController extends ChangeNotifier {
     );
   }
 
+  void setSelectionActionOrder(List<SelectionActionKind> order) {
+    _selectionActionOrder = order;
+    notifyListeners();
+    _prefsFuture.then(
+      (p) => p.setStringList(
+        _prefSelectionActionOrder,
+        order.map((k) => k.name).toList(),
+      ),
+    );
+  }
+
   /// Shows or hides a tab in the bottom nav bar. Refuses to hide the last
   /// remaining visible tab. If the tab being hidden is the current default,
   /// the default falls back to the next visible tab.