"Last week" metrics not served from 8-day warm cache

[alanpeixinho]

Problem

Warm cache stores 8-day entries for the 7- and 14-day windows every Saturday. The 14-day view hits it, but "last week" (7-day) keeps missing and falls back to fresh queries / 6h cache — slow on the most-used view.

Acceptance

After warm, both 7- and 14-day metrics* Redis keys show ~8-day TTL, and "last week" serves from cache all week.