[DOC] all: Reorganize and consolidate project documentation

- Create .github/copilot-instructions.md with global development guidelines
- Add comprehensive README.md at project root with quick start guide
- Create docs/ directory for technical documentation
- Move installation and linter docs to docs/
- Add docs/TRANSLATIONS.md with complete translation system guide
- Create README.md for OCA modified addons (product_origin, product_get_price_helper, product_main_seller)
- Document translation best practices (no _() in field definitions)
- Add references between all documentation files
- Clean up project root by moving technical docs to docs/

All documentation now properly references addon-specific READMEs for detailed architecture and implementation.

product_get_price_helper/README.md

@@ -0,0 +1,124 @@
+# Product Get Price Helper
+
+## Summary
+
+Provides a helper utility function to compute product prices with taxes, discounts, and unit of measure conversions.
+
+## Features
+
+- **Price Calculation Utility**: Helper method `get_product_price_for_pricelist`
+- **Tax Handling**: Automatically computes prices with or without taxes
+- **Discount Support**: Handles single and multiple discounts
+- **UoM Conversion**: Converts prices between different units of measure
+- **Reusable**: Can be used by other modules for price calculations
+
+## Technical Details
+
+### Utility Function
+
+Located in `utils.py`:
+
+```python
+def get_product_price_for_pricelist(
+    product,
+    qty,
+    pricelist,
+    partner=None,
+    uom=None,
+    date=None,
+    include_tax=False
+)
+```
+
+**Parameters**:
+- `product`: Product record (product.product or product.template)
+- `qty`: Quantity
+- `pricelist`: Pricelist to use for calculation
+- `partner`: Partner record (optional)
+- `uom`: Unit of measure (optional, uses product default if not provided)
+- `date`: Date for pricelist rules (optional, uses today if not provided)
+- `include_tax`: Boolean, whether to include taxes in the result
+
+**Returns**: Decimal price
+
+### How It Works
+
+1. Gets base price from pricelist
+2. Applies any applicable discounts
+3. Converts price if different UoM is specified
+4. Adds taxes if `include_tax=True`
+
+## Dependencies
+
+- `account` (Odoo core)
+- `product` (Odoo core)
+
+## Installation
+
+```bash
+docker-compose exec odoo odoo -d odoo -u product_get_price_helper --stop-after-init
+```
+
+## Usage
+
+### Example: Calculate Price with Tax
+
+```python
+from odoo.addons.product_get_price_helper.utils import get_product_price_for_pricelist
+
+price = get_product_price_for_pricelist(
+    product=product_record,
+    qty=10,
+    pricelist=pricelist_record,
+    partner=partner_record,
+    include_tax=True
+)
+```
+
+### Example: Calculate Price with Different UoM
+
+```python
+price = get_product_price_for_pricelist(
+    product=product_record,
+    qty=1,
+    pricelist=pricelist_record,
+    uom=kg_uom,  # Different from product's default UoM
+    include_tax=False
+)
+```
+
+## OCA Source
+
+- **Repository**: [product-attribute](https://github.com/OCA/product-attribute)
+- **Original Author**: ACSONE SA/NV
+- **License**: AGPL-3
+
+## Modifications for Kidekoop
+
+None - Used as-is from OCA.
+
+## Used By
+
+This helper is used by other modules in the project:
+- `product_sale_price_from_pricelist` - For automatic price calculations
+- `product_price_category` - For category-based pricing
+
+## Demo Data
+
+Includes demo data with:
+- Sample accounts
+- Sample pricelists
+
+Located in `demo/` directory.
+
+## Translations
+
+- ✅ Spanish (es)
+- ✅ Euskera (eu)
+
+Located in `i18n/` directory.
+
+---
+
+**Version**: 18.0.1.1.0
+**License**: AGPL-3