v0.6.27 — Climate time, combined range & maintenance due dates

Summary

Integrates community PRs from Pulpyyyy: flat Remaining climate time in minutes (#32), combined cruising range fallback for PHEVs (#30), and maintenance due date sensors with preserved interval sign (#35).

Flat remaining climate time (#32)

• Flat PHEVs deliver remaining_climatisation_time as minutes, not seconds.
• Entity registry migration resets stale s → min overrides on existing remaining_climate_time entities.

Combined cruising range (#30)

• When cruising_range_combined is empty but per-engine components are present, the sensor sums primary + secondary range. A usable portal value always wins.

Maintenance intervals (#35)

• Drops abs() so negative = remaining, positive = overdue.
• Adds Inspection due and Oil change due timestamp sensors.
• Raw day counters disabled by default; distance counters keep raw sign.

Test plan

• Flat PHEV: Remaining climate time shows minutes (e.g. 10 min, not 10 s)
• PHEV with empty combined range: Range (combined) equals primary + secondary
• Maintenance: due-date sensors show future/past dates; day counters show signed values when enabled