Feat: weekly email digest of coding activity summary

[diksha78dev]

Summary

Adds a new opt-in feature for users to receive a weekly email digest summarizing their coding habits. The feature introduces a new UI toggle in the settings and a secure Vercel Cron endpoint to handle dispatching emails via the Resend API.

Closes #1028

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor / code cleanup

Changes Made

Database : Added a migration to include weekly_digest_opt_in (boolean) and email (text) to the users Supabase table.
Auth: Updated NextAuth signIn callback to capture and save the user's email to the database on login.
Settings UI/API : Added a new "Weekly Email Digest" toggle in the Settings page and updated the GET / PATCH routes to support the new field.
Cron API: Created a secured /api/cron/weekly-digest route that queries opted-in users and sends HTML digests using a native fetch request to the Resend API (keeping dependencies small).
Vercel Config: Configured vercel.json with a cron schedule (0 9 * * 1 - every Monday at 9 AM UTC).
Testing Fix: Fixed a pre-existing duplicate test title in landing.spec.js that caused E2E test failures.

How to Test

Steps for the reviewer to verify this works:

1. Setup your local Supabase database and apply the new migration (or run npx supabase db reset).
2. Set RESEND_API_KEY (and optionally CRON_SECRET) in your local .env file.
3. Start the dev server (npm run dev), go to the Settings page, and toggle on the "Weekly Email Digest".
4. To test the cron job locally, execute the following command in your terminal (if using a cron secret, add -H "Authorization: Bearer YOUR_SECRET"): curl -X GET http://localhost:3000/api/cron/weekly-digest
5. Check your email inbox to verify the digest template was received successfully.

Screenshots (if UI change)

Checklist

• Linked issue in summary
• npm run lint passes locally
• No TypeScript errors (npm run type-check)
• Self-reviewed the diff
• Added/updated tests if applicable

[vercel]

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[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

Difficulty (pick one):

• level:beginner — 20 pts
• level:intermediate — 35 pts
• level:advanced — 55 pts
• level:critical — 80 pts

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• quality:exceptional — ×1.5 multiplier

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Type labels (type:*) are auto-detected from files and title. Review and adjust if needed.
Points formula: (difficulty × quality_multiplier) + type_bonus

[Priyanshu-byte-coder]

Good feature overall. One concern: adding email to the Supabase upsert in auth.ts will break sign-in for all users if the migration (20260526000000_add_weekly_digest_opt_in.sql) has not been run yet — PostgREST returns a 42703 error on unknown columns, which is not caught here.

Please add a try/catch around the email field or add the column to the migration before this can be safely merged. The rest of the feature (tiered settings with the 42703 fallback) is correctly handled.

[diksha78dev]

I'll make the required changes and resolve the conflicts..
Thanks for review..

[diksha78dev]

@Priyanshu-byte-coder i have resolved the merge conflicts .
Kindly review my PR.