[FIX] website_sale_aplicoop: Remove redundant string= attributes and fix OCA linting warnings

- Remove redundant string= from 17 field definitions where name matches string value (W8113)
- Convert @staticmethod to instance methods in selection methods for proper self.env._() access
- Fix W8161 (prefer-env-translation) by using self.env._() instead of standalone _()
- Fix W8301/W8115 (translation-not-lazy) by proper placement of % interpolation outside self.env._()
- Remove unused imports of odoo._ from group_order.py and sale_order_extension.py
- All OCA linting warnings in website_sale_aplicoop main models are now resolved

Changes:
- website_sale_aplicoop/models/group_order.py: 21 field definitions cleaned
- website_sale_aplicoop/models/sale_order_extension.py: 5 field definitions cleaned + @staticmethod conversion
- Consistent with OCA standards for addon submission

website_sale_aplicoop/static/src/js/i18n_helpers.js

@@ -1,30 +1,30 @@
 /**
  * DEPRECATED: Use i18n_manager.js instead
- * 
+ *
  * This file is kept for backwards compatibility only.
  * All translation logic has been moved to i18n_manager.js which
  * fetches translations from the server endpoint /eskaera/i18n
- * 
+ *
  * Migration guide:
  * OLD: window.getCheckoutLabels()
  * NEW: i18nManager.getAll()
- * 
+ *
  * OLD: window.formatCurrency(amount)
  * NEW: i18nManager.formatCurrency(amount)
- * 
+ *
  * Copyright 2025 Criptomart
  * License AGPL-3.0 or later
  */
 
-(function() {
-    'use strict';
+(function () {
+    "use strict";
 
     // Keep legacy functions as wrappers for backwards compatibility
-    
+
     /**
      * DEPRECATED - Use i18nManager.getAll() or i18nManager.get(key) instead
      */
-    window.getCheckoutLabels = function(key) {
+    window.getCheckoutLabels = function (key) {
         if (window.i18nManager && window.i18nManager.initialized) {
             if (key) {
                 return window.i18nManager.get(key);
@@ -38,30 +38,29 @@
     /**
      * DEPRECATED - Use i18nManager.getAll() instead
      */
-    window.getSearchLabels = function() {
+    window.getSearchLabels = function () {
         if (window.i18nManager && window.i18nManager.initialized) {
             return {
-                'searchPlaceholder': window.i18nManager.get('search_products'),
-                'noResults': window.i18nManager.get('no_results')
+                searchPlaceholder: window.i18nManager.get("search_products"),
+                noResults: window.i18nManager.get("no_results"),
             };
         }
         return {
-            'searchPlaceholder': 'Search products...',
-            'noResults': 'No products found'
+            searchPlaceholder: "Search products...",
+            noResults: "No products found",
         };
     };
 
     /**
      * DEPRECATED - Use i18nManager.formatCurrency(amount) instead
      */
-    window.formatCurrency = function(amount) {
+    window.formatCurrency = function (amount) {
         if (window.i18nManager) {
             return window.i18nManager.formatCurrency(amount);
         }
         // Fallback
-        return '€' + parseFloat(amount).toFixed(2);
+        return "€" + parseFloat(amount).toFixed(2);
     };
 
-    console.log('[i18n_helpers] DEPRECATED - Use i18n_manager.js instead');
-
+    console.log("[i18n_helpers] DEPRECATED - Use i18n_manager.js instead");
 })();