feat(tasks): Dual transport handlers and self-healing product_refresh

- Rename product-discovery.ts to product-discovery-curl.ts (axios-based)
- Rename payload-fetch.ts to payload-fetch-curl.ts
- Add product-discovery-http.ts (Puppeteer browser-based handler)
- Add method field to CreateTaskParams for transport selection
- Update task-service to insert method column on task creation
- Update task-worker with getHandlerForTask() for dual transport routing
- product_refresh now queues upstream tasks when no payload exists:
  - Has platform_dispensary_id → queues product_discovery (http)
  - No platform_dispensary_id → queues entry_point_discovery

This enables HTTP workers to pick up browser-based tasks while curl
workers handle axios-based tasks, and prevents product_refresh from
failing repeatedly when no crawl has been performed.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/tasks/handlers/index.ts

@@ -2,9 +2,15 @@
  * Task Handlers Index
  *
  * Exports all task handlers for the task worker.
+ *
+ * Product Discovery:
+ * - handleProductDiscoveryCurl: curl/axios based (for curl transport)
+ * - handleProductDiscoveryHttp: Puppeteer browser-based (for http transport)
  */
 
-export { handleProductDiscovery } from './product-discovery';
+export { handleProductDiscovery as handleProductDiscoveryCurl } from './product-discovery-curl';
+export { handleProductDiscoveryHttp } from './product-discovery-http';
+export { handlePayloadFetch as handlePayloadFetchCurl } from './payload-fetch-curl';
 export { handleProductRefresh } from './product-refresh';
 export { handleStoreDiscovery } from './store-discovery';
 export { handleEntryPointDiscovery } from './entry-point-discovery';