PRESIDECMS-3327: add relative between time period types

[jjannek]

Summary

• Adds two time period types, resolved at read time (dates are not frozen on save):
  • betweenago — from N units ago to M units ago (e.g. 48 hours ago → 24 hours ago)
  • betweenupcoming — from N units from now to M units from now (e.g. 24 hours from now → 48 hours from now)
• Honour pastOnly / futureOnly. Absolute between is unchanged. Inverted offsets are swapped so from is always earlier than to. measure2 = 0 means until/from now.

Fixes the gap where dashboard compares and rules-engine filters could not express a rolling window that does not end at now (today vs yesterday was the only calendar workaround).

Ticket: PRESIDECMS-3327

Test plan

• Unit tests in RulesEngineTimePeriodServiceTest (48h–24h, missing measure2, swapped offsets, invalid unit, future 24h–48h, omitted unit2)
• Admin: rules-engine date filter — choose between (relative past), 48 hours ago to 24 hours ago; confirm the configured label and that results match that window
• Admin: same with between (relative future) on a future date field
• Dashboard single-value widget with pastOnly: relative past appears, relative future does not
• Existing between (dates) and recently still work