Adds computeDistanceToHomeM() (mission_stats.dart) alongside the
existing rubber-band-target helper, wired through MissionFooterBar ->
BottomStatsBar the same way flyMissionStatus already is. Only appears
once a home point is known, as the last field after waypoint/distance/
duration.
Generalized HomePointIcon to take an optional strokeColor: the map
marker keeps its dark-fill-plus-white-outline look, while the details
pill uses a plain white fill (strokeColor: null) to match the existing
monochrome flag/ruler/clock icons instead of looking like a dropped-in
map pin.
Adds MSP_WP (118) support to query the flightcontroller's stored home
point (WP#0 is a special case for this in iNAV's getWaypoint(), per
navigation.c) - the FC reports (0,0,0) rather than an error before one
is set, so parseMspHomePoint() treats that pair as "unset". Rendered
with a small pentagon house icon (design/homepoint-pentagon.svg,
ported to a CustomPainter like the other map icons).
Deliberately not polled continuously: a new home_point_provider.dart
refreshes it only at the three moments the FC's home point can
actually change - connect/reconnect, GPS fix acquired, and arming
(iNAV's default reset_home_type=FIRST_ARM only freezes it at the first
arm; before that it continuously follows the aircraft while disarmed).
Mock's implementation offsets the point 25m from the anchor so it
doesn't sit exactly under the drone marker during UI testing.
Constantin Leue