fix(flight-planner): refresh stale home from vehicle

[obazna]

Summary

• refresh Flight Planner home from the reported vehicle HomeLocation whenever PLAN is selected or reselected
• fall back to PlannedHomeLocation, retaining the saved planner home only when neither vehicle coordinate is valid
• keep the official last-to-home-to-first route construction and styling unchanged

Verification

• FlightPlannerHomeSyncTests: 4/4 passed
• PlannerPortParityTests: 59/59 passed
• Release build: 0 warnings, 0 errors
• full Avalonia suite: 1561/1562 passed; only the existing host-sensitive /dev/video0 normalization case failed
• behavior, integration, and test reviewers approve exact HEAD b7994f9

Manual acceptance

Rebuild and relaunch this branch, connect a vehicle whose reported home differs from the saved planner home, select and reselect PLAN, and confirm the Home Location fields follow the vehicle before adding local waypoints.