API is running.

--- Infrastructure / diagnostics ---
  GET  /                        This index
  GET  /health                  Liveness probe — returns "ok"
  GET  /api                     JSON diagnostic info (config, URLs, issues)
  GET  /api/ready               Readiness — 200 if config valid, 400 if not
  GET  /api/check?shop=         Readiness for a specific shop (token + feature flags)
  GET  /api/redirect-url        Full OAuth redirect URL

--- Shopify OAuth ---
  GET  /install?shop=           Start OAuth — redirects to Shopify authorize URL
  GET  /oauth/callback           OAuth callback — code exchange, saves token, registers webhooks

--- Webhooks ---
  POST /webhooks/shopify        Shopify webhook receiver (products/*, orders/*)

--- DSS Internal API (X-DSS-Internal-Secret header required if configured) ---
  PUT  /stores/api-key                     Set Shopify Admin token (see repo openapi.json)
  POST /tracking-update                     Monolith webhook: SyncShipmentsWithFulfillmentsRequest → sync Shopify fulfillments
  POST /sync-shipments-with-fulfillments   Monolith webhook: TrackingUpdateRequest → Shopify FulfillmentEvent
  POST /tracking-updates                   Same TrackingUpdate body as .../sync-shipments-with-fulfillments (compat)

--- Demo routes (disabled — set ENABLE_DEMO_ROUTES=true) ---
  GET  /demo/products?shop=               List products via Shopify GraphQL
  GET  /demo/order?shop=&id=              Load a single order by GID or numeric ID
  POST /demo/fulfillment/create           Create a fulfillment with tracking
  POST /demo/fulfillment/tracking         Update fulfillment tracking info