Dashboard rolling 12 months

Status

DASHBOARD_12_MONTHS=IMPLEMENTED

The dashboard always displays the current calendar month plus the previous 11 months.

Empty months remain explicit empty positions on the X axis.

There is no zero filling and no line interpolation across a missing month.

When multiple observations exist in one month, the last observation of that month is used for the compact dashboard series.

No persistence or Trainlog JSON v1 changes are required.