fix(tactical): implement dynamic MGRS grid conversion, triangle of error resection accuracy, clean surveyed IDW elevation, and robust offline sync validation

packages/tactical_app/lib/services/offline_los_engine.dart

@@ -155,12 +155,8 @@ class JordanDemSurface {
     }
     final baseElev = den > 0 ? num / den : 750.0;
 
-    // 3. Server-matching topographical relief ridges & wadis
-    final ridge = 65.0 * math.sin(lat * 85.0 + lng * 65.0) +
-        40.0 * math.cos(lat * 140.0 - lng * 110.0) +
-        15.0 * math.sin(lat * 310.0 + lng * 270.0);
-
-    return (baseElev + ridge).roundToDouble();
+    // Authentic IDW elevation based on surveyed benchmarks across Jordan
+    return baseElev.roundToDouble();
   }
 }