Add sprint pulse, person timeline, trends, and cycle compare - #23

Summary

Implements the five history / mid-cycle analytics surfaces:

1. Sprint pulse (/sprint-pulse) — date-window coaching view with achievement / Jira / Bitbucket throughput, themes, concerns, and evidence freshness (stale-only cites)
2. Person timeline — chronological dossier + reviews + concerns + rating decisions on each person page
3. Rating trends — cross-cycle overall / competency team averages with sparklines on Team performance
4. Cycle compare — distribution shift, movers (±1+), repeat thin dossiers, theme drift
5. Evidence freshness — folded into sprint pulse (in-window vs older evidence + draft cite staleness)

Screenshots

Sprint pulse
Person timeline
Rating trends

APIs

• GET /api/sprint-pulse?preset=last_14|last_7|last_30 or from/to
• GET /api/people/:id/timeline
• GET /api/rating-trends
• GET /api/cycle-compare?cycleId=

Also

• Seed adds H2 2025 prior cycle with ratings, recent July window achievements (Jira/Bitbucket), themes, and a sample concern (fresh installs only)
• Unit tests for pure analytics builders
• Docs / README updates

How to try

Unlock → Sprint pulse (pick last 14 days or a custom range covering your dossier dates) → Team performance for trends/compare → open a person for Timeline.

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