fix: paginate weekly-digest cron query to prevent serverless timeout

[Meera2906]

Problem

The weekly-digest cron fetched all opted-in users in a single unbounded
Supabase query. With 200+ users and ~300ms per email send, the function
reliably exceeded Vercel's 60s timeout, causing partial delivery with no
retry mechanism.

Fix

Replaced the unbounded query with a paginated loop using .range():

• PAGE_SIZE = 50 rows fetched per Supabase query
• Existing BATCH_SIZE = 5 parallel email sends is preserved per page
• Each iteration stays well within the serverless timeout window
• totalFetched added to logs for observability

Fixes #1852

[github-actions]

GSSoC Label Checklist 🏷️

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

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[Priyanshu-byte-coder]

This PR has merge conflicts with the current main branch. Please rebase or merge main into your branch to resolve the conflicts, then push the updated branch. Once conflicts are resolved, this PR will be merged.

git fetch origin main
git merge origin/main
# resolve conflicts
git push

[Priyanshu-byte-coder]

CI is failing on the type check. Please fix the TypeScript errors and push again.

[Priyanshu-byte-coder]

Pagination logic has a bug: results is referenced outside the Promise.allSettled() call that defines it — the refactoring appears incomplete. The forEach over results is inside the pagination loop but results is never assigned. Please fix the scoping and rebase on main.

[Priyanshu-byte-coder]

This has merge conflicts with main. Please rebase/resolve conflicts and make sure CI is green — then it'll get a fresh review.

[Priyanshu-byte-coder]

The pagination idea is right (same fix I recently merged for the discord and wakatime cron jobs — #3190/#3203), but this branch doesn't compile: src/app/api/cron/weekly-digest/route.ts has syntax errors —

route.ts(334,13): error TS1128: Declaration or statement expected.
route.ts(349,7): error TS1005: ',' expected.

Fix the syntax so pnpm type-check passes, rebase on main (the weekly-digest route moved), and I'll review the pagination. Mirror the keyset/offset pattern from the discord-sync fix.

[Priyanshu-byte-coder]

Closing as stale. The last commit on this branch was 2026-06-17, over a month ago, and there's been no activity since. It also has merge conflicts against current main.

This isn't a rejection of the idea — DevTrack's PR queue grew past 110 open PRs, so I'm clearing branches that have gone quiet so the review tab reflects what's actually in progress.

If you still want to land this: rebase on current main, address any review feedback above, and reopen this PR (or open a fresh one) — I'll review it. Thanks for contributing to DevTrack.