feat: update API endpoints for company-vendor architecture

- Add transfer-ownership endpoint to companies API
- Add user search endpoint for autocomplete (/admin/users/search)
- Update company detail endpoint to include owner info and vendors list
- Update vendor endpoints to use company relationship for ownership
- Update deps.py vendor access check to use company.owner_user_id

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

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

app/api/v1/vendor/info.py

@@ -92,12 +92,7 @@ def get_vendor_info(
         subdomain=vendor.subdomain,
         name=vendor.name,
         description=vendor.description,
-        owner_user_id=vendor.owner_user_id,
-        contact_email=vendor.contact_email,
-        contact_phone=vendor.contact_phone,
-        website=vendor.website,
-        business_address=vendor.business_address,
-        tax_number=vendor.tax_number,
+        company_id=vendor.company_id,
         letzshop_csv_url_fr=vendor.letzshop_csv_url_fr,
         letzshop_csv_url_en=vendor.letzshop_csv_url_en,
         letzshop_csv_url_de=vendor.letzshop_csv_url_de,
@@ -105,7 +100,12 @@ def get_vendor_info(
         is_verified=vendor.is_verified,
         created_at=vendor.created_at,
         updated_at=vendor.updated_at,
-        # Owner details
-        owner_email=vendor.owner.email,
-        owner_username=vendor.owner.username,
+        # Company info
+        company_name=vendor.company.name,
+        company_contact_email=vendor.company.contact_email,
+        company_contact_phone=vendor.company.contact_phone,
+        company_website=vendor.company.website,
+        # Owner details (from company)
+        owner_email=vendor.company.owner.email,
+        owner_username=vendor.company.owner.username,
     )