ZOHO-WMS Shopify connector

Read-only Shopify inventory source scaffold for the future ZOHO-WMS to Zoho Inventory sync path.

• Read-only access. Uses product, inventory, and location scopes only.
• One-way inventory flow. Shopify inventory is source data for ZOHO-WMS; this app does not push stock back to Shopify.
• Not wired yet. Mapping approval and main backend handoff will be added in a later connector task.