Remove cron trigger implementation

- Remove cron-trigger.ts and cron-scheduler.ts files
- Clean up cron-related code from plugin index and workflow hooks
- Remove cron references from workflow executor types
- Add cron to NOT-IMPLEMENTING.md with webhook alternatives
- Update README with scheduled workflow documentation using external services
- Suggest GitHub Actions and Vercel Cron as reliable alternatives

Benefits of external scheduling:
- Better reliability and process isolation
- Easier debugging and monitoring
- Leverages existing cloud infrastructure
- Reduces plugin complexity and maintenance burden

src/plugin/init-workflow-hooks.ts

@@ -1,56 +1,12 @@
-import type {Payload} from 'payload'
-
-import {updateWorkflowCronJobs, removeWorkflowCronJobs} from './cron-scheduler.js'
+import type { Payload } from 'payload'
 
 /**
- * Initialize hooks for the workflows collection itself
- * to manage cron jobs when workflows are created/updated
+ * Initialize hooks for the workflows collection
+ * Currently minimal - can be extended for future workflow management features
  */
 export function initWorkflowHooks(payload: Payload, logger: Payload['logger']): void {
-  // Add afterChange hook to workflows collection to update cron jobs
-  const workflowsCollection = payload.collections.workflows
+  // Future workflow hooks can be added here
+  // For example: workflow validation, cleanup, statistics, etc.
   
-  if (!workflowsCollection) {
-    logger.warn('Workflows collection not found, cannot initialize workflow hooks')
-    return
-  }
-  
-  // Add afterChange hook to register/update cron jobs
-  if (!workflowsCollection.config.hooks?.afterChange) {
-    if (!workflowsCollection.config.hooks) {
-      // @ts-expect-error - hooks object will be populated by Payload
-      workflowsCollection.config.hooks = {}
-    }
-    workflowsCollection.config.hooks.afterChange = []
-  }
-  
-  workflowsCollection.config.hooks.afterChange.push(async ({ doc, operation }) => {
-    if (operation === 'create' || operation === 'update') {
-      logger.debug({
-        operation,
-        workflowId: doc.id,
-        workflowName: doc.name
-      }, 'Workflow changed, updating cron jobs selectively')
-      
-      // Update cron jobs for this specific workflow only
-      await updateWorkflowCronJobs(doc.id, payload, logger)
-    }
-  })
-  
-  // Add afterDelete hook to clean up cron jobs
-  if (!workflowsCollection.config.hooks?.afterDelete) {
-    workflowsCollection.config.hooks.afterDelete = []
-  }
-  
-  workflowsCollection.config.hooks.afterDelete.push(async ({ doc }) => {
-    logger.debug({
-      workflowId: doc.id,
-      workflowName: doc.name
-    }, 'Workflow deleted, removing cron jobs')
-    
-    // Remove cron jobs for the deleted workflow
-    removeWorkflowCronJobs(doc.id, payload, logger)
-  })
-  
-  logger.info('Workflow hooks initialized for cron job management')
+  logger.debug('Workflow hooks initialized')
 }