[ADD] product_main_seller: Restore OCA addon from original version

- Restored product_main_seller addon to fix dependency chain
- Addon required by product_origin_char and website_sale_aplicoop

[IMP] website_sale_aplicoop: Add demo data configuration to manifest

- Updated __manifest__.py to include demo data files
- Demo data includes partners, suppliers, products, group orders, and sale orders
- Demo data successfully loads during module installation

product_main_seller/i18n/product_main_seller.pot

@@ -0,0 +1,32 @@
+# Translation of Odoo Server.
+# This file contains the translation of the following modules:
+# 	* product_main_seller
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: Odoo Server 18.0\n"
+"Report-Msgid-Bugs-To: \n"
+"Last-Translator: \n"
+"Language-Team: \n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: \n"
+"Plural-Forms: \n"
+
+#. module: product_main_seller
+#: model:ir.model.fields,field_description:product_main_seller.field_product_product__main_seller_id
+#: model:ir.model.fields,field_description:product_main_seller.field_product_template__main_seller_id
+#: model_terms:ir.ui.view,arch_db:product_main_seller.view_product_template_search
+msgid "Main Vendor"
+msgstr ""
+
+#. module: product_main_seller
+#: model:ir.model,name:product_main_seller.model_product_template
+msgid "Product"
+msgstr ""
+
+#. module: product_main_seller
+#: model:ir.model.fields,help:product_main_seller.field_product_product__main_seller_id
+#: model:ir.model.fields,help:product_main_seller.field_product_template__main_seller_id
+msgid "Put your supplier info in first position to set as main vendor"
+msgstr ""