Bug: 30 days with 29 data points returned 'insufficient' because
it fell into the 90+ day branch which requires >= 30 data points.
Fix: Changed condition from 'days_requested <= 28' to 'days_requested < 90'
so that 8-89 day ranges use the medium-term thresholds:
- high >= 18 data points
- medium >= 12
- low >= 8
This means 30 days with 29 entries now returns 'high' confidence.
Affects: nutrition_avg, and all other medium-term metrics.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>