feat: add weekly email digest with AI productivity summary

[Subhra-Nandi]

[FEAT] Add weekly email digest with AI productivity summary

Closes #937

What this PR does

Implements the weekly email digest feature. Opted-in users receive a Monday 9am UTC email with an AI-generated productivity summary, current streak, top repo, PR stats, and a trend badge.

Changes

File	Description
supabase/migrations/20260529000000_add_digest_settings.sql	Adds digest_unsubscribe_token to users table
src/lib/digest.ts	AI summary generator + email HTML builder
src/app/api/settings/digest/route.ts	GET/POST opt-in preference API
src/app/api/cron/weekly-digest/route.ts	Enhanced with AI summary + unsubscribe token
src/components/DigestOptIn.tsx	Toggle switch component
src/app/settings/page.tsx	New /settings page
src/app/unsubscribe/page.tsx	Token-based one-click unsubscribe
src/components/DashboardHeader.tsx	Gear icon linking to /settings
.env.example	Documents new env vars

vercel.json already had the cron entry — no changes needed.

Acceptance Criteria

• User can opt in/out in Settings
• Cron triggers every Monday at 9am UTC
• Email compatible with Gmail, Outlook, Apple Mail
• Unsubscribe link in every email
• Unsubscribe works without login

Screenshots

Required before deploying

1. Run supabase/migrations/20260529000000_add_digest_settings.sql in Supabase SQL editor
2. Add env vars in Vercel: RESEND_API_KEY, RESEND_FROM_EMAIL, GEMINI_API_KEY, CRON_SECRET

[vercel]

@Subhra-Nandi is attempting to deploy a commit to the PRIYANSHU DOSHI's projects Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

GSSoC Label Checklist 🏷️

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

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• level:intermediate — 35 pts
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[github-actions]

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[Priyanshu-byte-coder]

This PR has merge conflicts with main. Please rebase your branch against the latest main and force-push to resolve. Run: git fetch upstream && git rebase upstream/main

[Priyanshu-byte-coder]

This PR has developed merge conflicts after recent merges to main. Please rebase onto the latest main branch, resolve all conflicts, and force-push. Once the PR is conflict-free it will be reviewed for merging.

[Priyanshu-byte-coder]

This PR has merge conflicts with the current main branch. Please rebase on the latest main to resolve them — your contribution is labeled for GSSoC scoring.

[Priyanshu-byte-coder]

This PR has merge conflicts with main due to recent changes. Please rebase to continue:

git fetch origin
git rebase origin/main

Once you resolve the conflicts and CI passes, we can review for merge.

[Priyanshu-byte-coder]

Hi! This PR has merge conflicts with the main branch. Could you please rebase or merge main into your branch to resolve them? We'd love to get this merged! 🚀

git fetch upstream
git rebase upstream/main
# resolve any conflicts
git push --force-with-lease

If you're no longer working on this, let us know and we can close it. Thanks!

[Subhra-Nandi]

Hi! Thanks for the heads-up. I won't be able to dedicate time to finish up the rebase or work on this feature further right now, so please feel free to close this pull request. Thanks for your time and guidance!

[Priyanshu-byte-coder]

This PR has merge conflicts with the main branch. Please rebase your branch on latest main and resolve the conflicts so it can be reviewed and merged.