fix: clamp los profile bounds

lib/l10n/app_en.arb

@@ -1673,7 +1673,7 @@
   "losFrequencyLabel": "Frequency",
   "losFrequencyInfoTooltip": "View calculation details",
   "losFrequencyDialogTitle": "Radio horizon calculation",
-  "losFrequencyDialogDescription": "Starting from k={baselineK} at {baselineFreq} MHz, the calculation multiplies 0.15 × (frequency − {baselineFreq}) / {baselineFreq} to reach k approx {kFactor} for the current {frequencyMHz} MHz band, which defines the curved radio horizon cap.",
+  "losFrequencyDialogDescription": "Starting from k={baselineK} at {baselineFreq} MHz, the calculation adjusts the k-factor for the current {frequencyMHz} MHz band, which defines the curved radio horizon cap.",
   "@losFrequencyDialogDescription": {
     "description": "Explain how the calculation uses the baseline frequency and derived k-factor.",
     "placeholders": {

lib/l10n/app_localizations.dart

@@ -5043,7 +5043,7 @@ abstract class AppLocalizations {
   /// Explain how the calculation uses the baseline frequency and derived k-factor.
   ///
   /// In en, this message translates to:
-  /// **'Starting from k={baselineK} at {baselineFreq} MHz, the calculation multiplies 0.15 × (frequency − {baselineFreq}) / {baselineFreq} to reach k approx {kFactor} for the current {frequencyMHz} MHz band, which defines the curved radio horizon cap.'**
+  /// **'Starting from k={baselineK} at {baselineFreq} MHz, the calculation adjusts the k-factor for the current {frequencyMHz} MHz band, which defines the curved radio horizon cap.'**
   String losFrequencyDialogDescription(
     double baselineK,
     double baselineFreq,

lib/l10n/app_localizations_en.dart

@@ -2849,7 +2849,7 @@ class AppLocalizationsEn extends AppLocalizations {
     double frequencyMHz,
     double kFactor,
   ) {
-    return 'Starting from k=$baselineK at $baselineFreq MHz, the calculation multiplies 0.15 × (frequency − $baselineFreq) / $baselineFreq to reach k approx $kFactor for the current $frequencyMHz MHz band, which defines the curved radio horizon cap.';
+    return 'Starting from k=$baselineK at $baselineFreq MHz, the calculation adjusts the k-factor for the current $frequencyMHz MHz band, which defines the curved radio horizon cap.';
   }
 
   @override

lib/screens/line_of_sight_map_screen.dart

@@ -1065,13 +1065,15 @@ class _LosProfilePainter extends CustomPainter {
       samples.last.terrainMeters,
     );
 
-    double distanceForCanvasX(double x) =>
+    double distanceForCanvasX(double x) {
-        ((x - horizontalPadding) / chartWidth) * maxDist;
+      final normalized = ((x - horizontalPadding) / chartWidth).clamp(0.0, 1.0);
+      return normalized * maxDist;
+    }
 
-    double elevationToPixel(double elevation) =>
+    double elevationToPixel(double elevation) {
-        size.height -
+      final normalized = ((elevation - minY) / ySpan).clamp(0.0, 1.0);
-        verticalPadding -
+      return size.height - verticalPadding - normalized * chartHeight;
-        ((elevation - minY) / ySpan) * chartHeight;
+    }
 
     double extrapolateTerrain(double distance, bool isLeft) {
       final samplesForSlope = isLeft