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/index.ts

@@ -11,9 +11,9 @@ export { MailingService } from './services/MailingService.js'
 export { default as EmailTemplates, createEmailTemplatesCollection } from './collections/EmailTemplates.js'
 export { default as Emails } from './collections/Emails.js'
 
-// Jobs (includes the send email task)
-export { mailingJobs, sendEmailJob } from './jobs/index.js'
-export type { SendEmailTaskInput } from './jobs/sendEmailTask.js'
+// Jobs (includes the individual email processing job)
+export { mailingJobs } from './jobs/index.js'
+export type { ProcessEmailJobInput } from './jobs/processEmailJob.js'
 
 // Main email sending function
 export { sendEmail, type SendEmailOptions } from './sendEmail.js'