[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/models/res_partner_extension.py

@@ -1,37 +1,39 @@
 # Copyright 2025-Today Criptomart
 # License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl)
 
-from odoo import _, fields, models
+from odoo import _
+from odoo import fields
+from odoo import models
 
 
 class ResPartner(models.Model):
-    _inherit = 'res.partner'
+    _inherit = "res.partner"
 
     # Campo para identificar si un partner es un grupo
     is_group = fields.Boolean(
-        string='Is a Consumer Group?',
-        help='Check this box if the partner represents a group of users',
+        string="Is a Consumer Group?",
+        help="Check this box if the partner represents a group of users",
         default=False,
     )
 
     # Relación para los miembros de un grupo (si is_group es True)
     member_ids = fields.Many2many(
-        'res.partner',
-        'res_partner_group_members_rel',
-        'group_id',
-        'member_id',
-        domain=[('is_group', '=', True)],
-        string='Consumer Groups',
-        help='Consumer Groups this partner belongs to',
+        "res.partner",
+        "res_partner_group_members_rel",
+        "group_id",
+        "member_id",
+        domain=[("is_group", "=", True)],
+        string="Consumer Groups",
+        help="Consumer Groups this partner belongs to",
     )
 
     # Inverse relation: group orders this group participates in
     group_order_ids = fields.Many2many(
-        'group.order',
-        'group_order_group_rel',
-        'group_id',
-        'order_id',
-        string='Consumer Group Orders',
-        help='Group orders this consumer group participates in',
+        "group.order",
+        "group_order_group_rel",
+        "group_id",
+        "order_id",
+        string="Consumer Group Orders",
+        help="Group orders this consumer group participates in",
         readonly=True,
     )