feat(tier1): add reactions, recents, auto-archive, burndown and relation alerts

[parth0025]

Summary

Tier 1 of the roadmap (small, visible gaps every Plane/Jira evaluator checks) on a single branch — five enhancements, plus the discovery that two more were already shipped.

What''s included

Feature	Scope
Emoji reactions on comments	New Modules/Reactions (POST /api/v2/reactions, allowlisted GitHub-style emoji set, toggle semantics, socket emits on the right channels); reactions arrays on the strict tasks + comments schemas; ReactionBar component under every comment bubble with a viewport-clamped, teleported picker
Recently visited	New recentVisits collection (full schema/collection plumbing + indexes); visits auto-recorded on task open; Recent dropdown in the board toolbar, newest first, click navigates straight to the task
Auto-archive rules	Per-project autoArchive {enabled, afterDays}; GET/POST /api/v1/projectSetting/autoArchive; nightly cron (01:00 UTC) archiving completed tasks untouched for N days — children, sprint counters, history, socket emits handled; 200 tasks/project/run safety cap. Backend only — settings UI is a follow-up
Sprint burndown	Read-only POST /api/v2/sprints/burndown computing daily remaining-vs-ideal from existing status history + estimates; Burndown toolbar button with sprint-picker modal + ApexCharts line chart
Relation follow-ups	Watcher notifications on link/unlink through the existing pipeline; warning toast when completing a task still blocked by open tasks (single updateStatus chokepoint)

Found already shipped, untouched: task + project favorites, watchers (incl. task-level watcher UI).

Also: toolbar fitted to a single line (search block now shrinks to content), reaction picker immune to overflow clipping.

Testing

• Unit tests — 18 new (12 reaction rules, 6 auto-archive rules); full suite 63/63 green
• Manual testing — reactions, recents, burndown, toolbar verified in the browser on a live project; UI feedback rounds already incorporated
• Integration tests

Scope of Change

• Frontend
• Backend
• API
• Database
• Infrastructure
• Documentation

Breaking Changes

• No — purely additive (new modules, new schema fields with safe defaults, new toolbar controls). Note: the auto-archive cron only registers when NODE_ENV=production.

📝 Additional Notes

• Auto-archive settings toggle UI is the one deliberate follow-up.
• Commit subject kept parser-plain per the release-please lesson.

🤖 Generated with Claude Code

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