Implement scoring decay and scheduled refresh

Steps

1. Define half-lives. Per signal type: how long does relevance last?
2. Build decay function. Exponential decay applied to signal-weighted scores.
3. Schedule recalculation. Weekly job recalculates all scores.
4. Sync to CRM. Updated scores with change indicators.
5. Validate. Reps report scores match their intuition about account timing.

Success criteria

Stale-signal accounts drop in ranking within 2 weeks. Rep trust in scores increases.