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/schema/vendor_product.py

@@ -85,7 +85,7 @@ class VendorProductDetail(BaseModel):
     vendor_id: int
     vendor_name: str | None = None
     vendor_code: str | None = None
-    marketplace_product_id: int
+    marketplace_product_id: int | None = None  # Optional for direct product creation
     vendor_sku: str | None = None
     # Product identifiers
     gtin: str | None = None
@@ -149,10 +149,46 @@ class RemoveProductResponse(BaseModel):
     message: str
 
 
+class TranslationUpdate(BaseModel):
+    """Translation data for a single language."""
+
+    title: str | None = None
+    description: str | None = None
+
+
 class VendorProductCreate(BaseModel):
-    """Schema for creating a vendor product."""
+    """Schema for creating a vendor product (admin use - includes vendor_id)."""
 
     vendor_id: int
+
+    # Translations by language code (en, fr, de, lu)
+    translations: dict[str, TranslationUpdate] | None = None
+
+    # Product identifiers
+    brand: str | None = None
+    vendor_sku: str | None = None
+    gtin: str | None = None
+    gtin_type: str | None = None  # ean13, ean8, upc, isbn
+
+    # Pricing
+    price: float | None = None
+    sale_price: float | None = None
+    currency: str = "EUR"
+    tax_rate_percent: int | None = 17  # Default Luxembourg VAT
+    availability: str | None = None
+
+    # Image
+    primary_image_url: str | None = None
+
+    # Status
+    is_active: bool = True
+    is_featured: bool = False
+    is_digital: bool = False
+
+
+class VendorDirectProductCreate(BaseModel):
+    """Schema for vendor direct product creation (vendor_id from JWT token)."""
+
     title: str
     brand: str | None = None
     vendor_sku: str | None = None
@@ -162,14 +198,6 @@ class VendorProductCreate(BaseModel):
     availability: str | None = None
     is_active: bool = True
     is_featured: bool = False
-    is_digital: bool = False
-    description: str | None = None
-
-
-class TranslationUpdate(BaseModel):
-    """Translation data for a single language."""
-
-    title: str | None = None
     description: str | None = None
 
 
@@ -190,8 +218,10 @@ class VendorProductUpdate(BaseModel):
     sale_price: float | None = None  # Optional sale price
     currency: str | None = None
     tax_rate_percent: int | None = None  # 3, 8, 14, 17
+    availability: str | None = None  # in_stock, out_of_stock, preorder, backorder
 
-    # Status (is_digital is derived from marketplace product, not editable)
+    # Status
+    is_digital: bool | None = None
     is_active: bool | None = None
     is_featured: bool | None = None