Remove deprecated processEmailsTask and associated helpers

- Deleted batch email processing logic in favor of individual email jobs
- Updated `mailingJobs` to only register `processEmailJob`
- Simplified LiquidJS initialization check in `MailingService`
- Bumped version to 0.4.13

src/services/MailingService.ts

@@ -366,7 +366,7 @@ export class MailingService implements IMailingService {
     if (engine === 'liquidjs') {
       try {
         await this.ensureLiquidJSInitialized()
-        if (this.liquid && typeof this.liquid !== 'boolean') {
+        if (this.liquid) {
           return await this.liquid.parseAndRender(template, variables)
         }
       } catch (error) {