Delete AetheriaMath in favour of CultMath

AetheriaMath predates the CultMath swap and re-implemented helpers CultMath
now owns. Callers use CultMath directly: decay (Ship, AetherDrive, Entity),
damp (VelocityConversion, FieldTester, FieldDriver), first_order_intercept
(TurretController, Combat, GuidedProjectile), quadratic_bezier (FieldDriver)
and smootherstep (Ship). Parameter order matches in every case, and those
formulas have the same float evaluation order, so behaviour is unchanged.
Galaxy's commented-out segment check names distance_to_segment.

The other overloads had no callers and are dropped without a CultMath
counterpart being needed: the double Damp overloads, FindDistanceToSegment,
GetCatmullRomPosition, GetCubicSplinePosition, Smoothstep(x), and the
Deg2Rad/Rad2Deg constants.

AetherDb census, factions and hardpoint-fit are byte-identical to the
pre-cut captures.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/Entity.cs

@@ -855,7 +855,7 @@ public abstract class Entity
 
         foreach (var v in VisibilitySources.Keys.ToArray())
         {
-            VisibilitySources[v] = AetheriaMath.Decay(VisibilitySources[v], ItemManager.GameplaySettings.VisibilityDecay, delta);
+            VisibilitySources[v] = decay(VisibilitySources[v], ItemManager.GameplaySettings.VisibilityDecay, delta);
  
             if (VisibilitySources[v] < 0.1f) VisibilitySources.Remove(v);
         }