Add a custom "back" button to refreshable state

- Long press to return to the "home" screen

lib/inventree/stock.dart

@@ -473,6 +473,7 @@ class InvenTreeStockItem extends InvenTreeModel {
     return response.isValid();
   }
 
+  // TODO: Refactor this once the server supports API metadata for this action
   Future<bool> countStock(BuildContext context, double q, {String? notes}) async {
 
     final bool result = await adjustStock(context, "/stock/count/", q, notes: notes);
@@ -480,6 +481,7 @@ class InvenTreeStockItem extends InvenTreeModel {
     return result;
   }
 
+  // TODO: Refactor this once the server supports API metadata for this action
   Future<bool> addStock(BuildContext context, double q, {String? notes}) async {
 
     final bool result = await adjustStock(context,  "/stock/add/", q, notes: notes);
@@ -487,6 +489,7 @@ class InvenTreeStockItem extends InvenTreeModel {
     return result;
   }
 
+  // TODO: Refactor this once the server supports API metadata for this action
   Future<bool> removeStock(BuildContext context, double q, {String? notes}) async {
 
     final bool result = await adjustStock(context, "/stock/remove/", q, notes: notes);
@@ -494,6 +497,7 @@ class InvenTreeStockItem extends InvenTreeModel {
     return result;
   }
 
+  // TODO: Refactor this once the server supports API metadata for this action
   Future<bool> transferStock(int location, {double? quantity, String? notes}) async {
     if ((quantity == null) || (quantity < 0) || (quantity > this.quantity)) {
       quantity = this.quantity;

lib/widget/back.dart

@@ -0,0 +1,27 @@
+/*
+ * A custom implementation of a "Back" button for display in the app drawer
+ *
+ * Long-pressing on this will return the user to the home screen
+ */
+
+import "package:flutter/cupertino.dart";
+import "package:flutter/material.dart";
+
+Widget backButton(BuildContext context) {
+
+  return GestureDetector(
+    onLongPress: () {
+      while (Navigator.of(context).canPop()) {
+        Navigator.of(context).pop();
+      }
+    },
+    child: IconButton(
+      icon: BackButtonIcon(),
+      onPressed: () {
+        if (Navigator.of(context).canPop()) {
+          Navigator.of(context).pop();
+        }
+      },
+    ),
+  );
+}

lib/widget/refreshable_state.dart

@@ -1,3 +1,4 @@
+import 'package:inventree/widget/back.dart';
 import "package:inventree/widget/drawer.dart";
 import "package:flutter/cupertino.dart";
 import "package:flutter/material.dart";
@@ -66,6 +67,7 @@ abstract class RefreshableState<T extends StatefulWidget> extends State<T> {
     return AppBar(
       title: Text(getAppBarTitle(context)),
       actions: getAppBarActions(context),
+      leading: backButton(context),
     );
   }