[ADD] product_origin_char: Free text origin field per supplier

New addon to replace structured country/state fields with flexible
free-text origin descriptions.

Features:
- Translatable origin_text field in product.supplierinfo
- Computed origin field in products based on main_seller_id
- Support for creative supplier origin descriptions
- Full OCA documentation structure
- ES/EU translations included
- 8 unit tests (all passing)

Replaces product_origin for use cases where suppliers use non-standardized
origin descriptions (e.g., 'Valencia, Spain', 'Huerta de...', etc.)

Depends on: product, product_main_seller
Author: Criptomart
Funding: Elika Bilbo

product_origin_char/readme/DESCRIPTION.rst

@@ -0,0 +1,34 @@
+This module replaces the structured country/state origin fields from ``product_origin``
+with a flexible free-text field that can be defined per supplier.
+
+**Problem:**
+
+The standard ``product_origin`` module provides structured fields (country + state) for
+product origin. However, suppliers often use creative and varied formats to describe
+product origin:
+
+* "Valencia, Spain"
+* "Huerta de Ana, Aragón"
+* "Organic Farm - Northern Italy"
+* "Local producer - Basque Country"
+* "Fair Trade - Colombia"
+
+These free-form descriptions don't fit into structured country/state fields.
+
+**Solution:**
+
+This module adds a translatable ``origin_text`` field to ``product.supplierinfo`` that:
+
+* Allows free-form text to describe product origin
+* Is stored per supplier (different suppliers may have different origin info)
+* Is translatable (can be described differently in each language)
+* Is automatically displayed on the product based on the main vendor
+  (from ``product_main_seller`` module)
+
+**Features:**
+
+* Free-text ``Origin`` field in supplier info (Purchase tab of product)
+* Computed ``Origin`` field in product form (shows main vendor's origin)
+* Field is visible in product list view (optional column)
+* Full translation support for multiple languages
+* Compatible with existing supplier management workflows