Consolidate and simplify email job system

- Replace inline plugin task with jobs directory system
- Move sendTemplateEmailTask to jobs/sendEmailTask.ts and integrate with createMailingJobs()
- Simplify processEmailsJob to always process both pending and failed emails in one task
- Remove separate 'retry-failed' task type - retry logic now runs automatically
- Update MailingService to support lazy initialization for job context
- Update exports to include consolidated job system

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

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

src/jobs/index.ts

@@ -1,4 +1,5 @@
 import { processEmailsJob, ProcessEmailsJobData } from './processEmailsJob.js'
+import { sendEmailJob } from './sendEmailTask.js'
 import { MailingService } from '../services/MailingService.js'
 
 export const createMailingJobs = (mailingService: MailingService): any[] => {
@@ -13,7 +14,9 @@ export const createMailingJobs = (mailingService: MailingService): any[] => {
       },
       interfaceName: 'ProcessEmailsJob',
     },
+    sendEmailJob,
   ]
 }
 
-export * from './processEmailsJob.js'
+export * from './processEmailsJob.js'
+export * from './sendEmailTask.js'