Flatten email processing structure to individual jobs per email

BREAKING CHANGE: Replaced batch email processing with individual jobs per email

Changes:
- Remove sendEmailTask.ts - no longer needed as each email gets its own job
- Add processEmailJob.ts - handles individual email processing
- Update sendEmail() to automatically create individual job per email
- Add processImmediately option to sendEmail() for instant processing
- Add processJobById() utility to run specific jobs immediately
- Update job registration to use new individual job structure
- Update dev API routes to use new processImmediately pattern
- Fix all TypeScript compilation errors

Benefits:
- Better job queue visibility (one job per email)
- More granular control over individual email processing
- Easier job monitoring and failure tracking
- Maintains backward compatibility via processImmediately option
- Simpler job queue management

Migration:
- Replace sendEmailJob usage with sendEmail({ processImmediately: true })
- Individual emails now appear as separate jobs in queue
- Batch processing still available via processEmailsTask if needed

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

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

src/jobs/processEmailJob.ts

@@ -0,0 +1,78 @@
+import type { PayloadRequest } from 'payload'
+import { processEmailById } from '../utils/emailProcessor.js'
+
+/**
+ * Data passed to the individual email processing job
+ */
+export interface ProcessEmailJobInput {
+  /**
+   * The ID of the email to process
+   */
+  emailId: string | number
+}
+
+/**
+ * Job definition for processing a single email
+ * This replaces the batch processing approach with individual email jobs
+ */
+export const processEmailJob = {
+  slug: 'process-email',
+  label: 'Process Individual Email',
+  inputSchema: [
+    {
+      name: 'emailId',
+      type: 'text' as const,
+      required: true,
+      label: 'Email ID',
+      admin: {
+        description: 'The ID of the email to process and send'
+      }
+    }
+  ],
+  outputSchema: [
+    {
+      name: 'success',
+      type: 'checkbox' as const
+    },
+    {
+      name: 'emailId',
+      type: 'text' as const
+    },
+    {
+      name: 'status',
+      type: 'text' as const
+    }
+  ],
+  handler: async ({ input, req }: { input: ProcessEmailJobInput; req: PayloadRequest }) => {
+    const payload = (req as any).payload
+    const { emailId } = input
+
+    if (!emailId) {
+      throw new Error('Email ID is required for processing')
+    }
+
+    try {
+      // Process the individual email
+      await processEmailById(payload, String(emailId))
+
+      return {
+        output: {
+          success: true,
+          emailId: String(emailId),
+          status: 'sent',
+          message: `Email ${emailId} processed successfully`
+        }
+      }
+    } catch (error) {
+      // Re-throw Error instances to preserve stack trace and error context
+      if (error instanceof Error) {
+        throw error
+      } else {
+        // Only wrap non-Error values
+        throw new Error(`Failed to process email ${emailId}: ${String(error)}`)
+      }
+    }
+  }
+}
+
+export default processEmailJob