feat: make Product fully independent from MarketplaceProduct

- Add is_digital and product_type columns to Product model
- Remove is_digital/product_type properties that derived from MarketplaceProduct
- Update Create form with translation tabs, GTIN type, sale price, VAT rate, image
- Update Edit form to allow editing is_digital (remove disabled state)
- Add Availability field to Edit form
- Fix Detail page for directly created products (no marketplace source)
- Update vendor_product_service to handle new fields in create/update
- Add VendorProductCreate/Update schema fields for translations and is_digital
- Add unit tests for is_digital column and direct product creation
- Add integration tests for create/update API with new fields
- Create product-architecture.md documenting the independent copy pattern
- Add migration y3d4e5f6g7h8 for is_digital and product_type columns

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/database/product.py

@@ -1,11 +1,11 @@
 """Vendor Product model - independent copy pattern.
 
-This model represents a vendor's copy of a marketplace product. Products are
-independent entities with all fields populated at creation time from the source
-marketplace product.
+This model represents a vendor's product. Products can be:
+1. Created from a marketplace import (has marketplace_product_id)
+2. Created directly by the vendor (no marketplace_product_id)
 
-The marketplace_product_id FK is kept for "view original source" feature,
-allowing comparison with the original marketplace data.
+When created from marketplace, the marketplace_product_id FK provides
+"view original source" comparison feature.
 
 Money values are stored as integer cents (e.g., €105.91 = 10591).
 See docs/architecture/money-handling.md for details.
@@ -29,11 +29,10 @@ from models.database.base import TimestampMixin
 
 
 class Product(Base, TimestampMixin):
-    """Vendor-specific product - independent copy.
+    """Vendor-specific product.
 
-    Each vendor has their own copy of a marketplace product with all fields
-    populated at creation time. The marketplace_product_id FK is kept for
-    "view original source" comparison feature.
+    Products can be created from marketplace imports or directly by vendors.
+    When from marketplace, marketplace_product_id provides source comparison.
 
     Price fields use integer cents for precision (€19.99 = 1999 cents).
     """
@@ -43,7 +42,7 @@ class Product(Base, TimestampMixin):
     id = Column(Integer, primary_key=True, index=True)
     vendor_id = Column(Integer, ForeignKey("vendors.id"), nullable=False)
     marketplace_product_id = Column(
-        Integer, ForeignKey("marketplace_products.id"), nullable=False
+        Integer, ForeignKey("marketplace_products.id"), nullable=True
     )
 
     # === VENDOR REFERENCE ===
@@ -85,7 +84,11 @@ class Product(Base, TimestampMixin):
     cost_cents = Column(Integer)  # What vendor pays to acquire (in cents) - for profit calculation
     margin_percent_x100 = Column(Integer)  # Markup percentage * 100 (e.g., 25.5% = 2550)
 
-    # === VENDOR-SPECIFIC (No inheritance) ===
+    # === PRODUCT TYPE ===
+    is_digital = Column(Boolean, default=False, index=True)
+    product_type = Column(String(20), default="physical")  # physical, digital, service, subscription
+
+    # === VENDOR-SPECIFIC ===
     is_featured = Column(Boolean, default=False)
     is_active = Column(Boolean, default=True)
     display_order = Column(Integer, default=0)
@@ -249,20 +252,6 @@ class Product(Base, TimestampMixin):
             return None
         return round((profit / net) * 100, 2)
 
-    # === MARKETPLACE PRODUCT PROPERTIES ===
-
-    @property
-    def is_digital(self) -> bool:
-        """Check if this is a digital product."""
-        mp = self.marketplace_product
-        return mp.is_digital if mp else False
-
-    @property
-    def product_type(self) -> str:
-        """Get product type from marketplace product."""
-        mp = self.marketplace_product
-        return mp.product_type_enum if mp else "physical"
-
     # === INVENTORY PROPERTIES ===
 
     # Constant for unlimited inventory (digital products)
@@ -305,6 +294,7 @@ class Product(Base, TimestampMixin):
 
         Returns a dict with current field values and original source values
         from the marketplace product. Used for "view original source" feature.
+        Only populated when product was created from a marketplace source.
         """
         mp = self.marketplace_product
         return {
@@ -331,7 +321,7 @@ class Product(Base, TimestampMixin):
             # Images
             "primary_image_url": self.primary_image_url,
             "primary_image_url_source": mp.image_link if mp else None,
-            # Product type info
+            # Product type (independent fields, no source comparison)
             "is_digital": self.is_digital,
             "product_type": self.product_type,
         }