feat: add Inngest stage automation workflow

[StefanoFalco]

Related Issue:

No linked issue for now. This PR addresses the migration of part of the recruitment stage automation flow from n8n to Inngest.

Description:

This PR introduces an Inngest-based automation layer for selected recruitment stage transitions, moving part of the current n8n-driven flow closer to the Next.js application.

The implemented changes include:

• added an Inngest client and a Next.js API route for Inngest under the existing /recruitment base path;
• added shared stage events for triggering and canceling delayed automations;
• implemented a shared scheduling rule with Rome timezone support and sleeping-hour handling;
• added delayed Inngest functions for Stage A, Stage B, and Stage C;
• added cancellation support for pending stage workflows through cancellation events;
• added shared automation utilities for Telegram notifications, email sending, Google Docs template rendering, and stage data loading;
• updated stage switching logic so stage changes emit Inngest events directly from the app;
• updated initial applicant creation so Stage A can also be triggered by the app rather than only through n8n;
• added dry-run support to safely test the flow without actually sending emails or Telegram messages.

Stage D has intentionally not yet been fully migrated in this PR, because it involves more complex persistent side effects such as Google Docs report creation, Google Calendar event creation, Google Meet generation, and saving generated data back into the interview record. This will be handled in a follow-up PR after validating the basic Inngest structure.

Validation:

• I ran pnpm lint.
• I successfully ran pnpm build.
• I ran pnpm dev and checked the local Next.js app.
• I tested /recruitment/api/inngest-health.
• I tested /recruitment/api/inngest.
• I started the Inngest dev server against /recruitment/api/inngest.
• I verified that the PR targets dev and not main.
• I checked that the branch follows the requested naming format.
• I reviewed the generated AI-assisted code before submitting.

[pasc4le]

@all-contributors please add @StefanoFalco for code

[allcontributors]

@pasc4le

I've put up a pull request to add @StefanoFalco! 🎉

[StefanoFalco]

I also pushed the follow-up Stage D branch:

StefanoFalco/inngest-stage-d-automation

I am not opening it as a separate PR to dev yet, because it depends on this current Inngest A/B/C PR. Once this PR is reviewed and merged into dev, I will rebase the Stage D branch on top of the updated dev and open a clean second PR.

Stage D adds the Inngest workflow for creating the interview report document, creating the Google Calendar event with Google Meet link, saving meetingId and reportDocId back into the interview record, and notifying HR.

[pasc4le]

Excellent PR! Thank you for the submission. I'm only concerned about the sleepUntil, won't it cause unnecessary CPU load? I saw on the documentation that there's also a way to schedule one-off tasks:

https://www.inngest.com/docs/examples/scheduling-one-off-function

Should we think about switching to this solution instead?

P.S. Upon further thinking, it's fine this way, better not to delay this uselessly. Just check the all-contributors-cli dep and we should be good to go.

[StefanoFalco]

Ok, I kept sleepUntil as discussed, since Inngest handles it as a durable wait, and it should not create CPU load in the Next.js process.
I pushed a small follow-up commit that should solve the issues/redundancies that emerged.