fix(vendor): show company values in business details placeholders

Added company_business_address and company_tax_number to:
- VendorDetailResponse schema
- API response builder

Template now shows actual company values as placeholders instead of
generic "Using company address/tax number" text.

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

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

models/schema/vendor.py

@@ -188,6 +188,8 @@ class VendorDetailResponse(VendorResponse):
     company_contact_email: str | None = Field(None, description="Company's contact email")
     company_contact_phone: str | None = Field(None, description="Company's phone number")
     company_website: str | None = Field(None, description="Company's website URL")
+    company_business_address: str | None = Field(None, description="Company's business address")
+    company_tax_number: str | None = Field(None, description="Company's tax number")
 
 
 class VendorCreateResponse(VendorDetailResponse):