Palette: seven roles (accent, good, caution added; highlight renamed alarm); no hard-coded colours left

background, foreground, subdued, accent (emphasis without danger), and the state
gradient good → caution → alarm; surface and onFill derived. smart-serow's
four-key themes still load (highlight = alarm; the new roles fall back).
Material's scheme follows: buttons in accent instead of the alarm colour.
Link state, mock banner, signal tiles, raw log, checklist button and marks,
camera page all take palette roles.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

lib/widgets/gps_compass.dart

@@ -50,7 +50,8 @@ class GpsCompass extends StatelessWidget {
     final theme = AppTheme.of(context);
 
     // No signal = subdued color, valid = foreground
-    final iconColour = _hasSignal ? theme.foreground : theme.highlight;
+    // Heading: foreground; acquiring: caution; no receiver at all: alarm.
+    final iconColour = _hasSignal ? theme.foreground : (_isAcquiring ? theme.caution : theme.alarm);
 
     // Convert to radians, 0 = no rotation when no signal
     final angle = _hasSignal ? (heading! * math.pi / 180.0) : 0.0;