Radar ping taunt sound + per-SoundEffect spatialize opt-in

MatchManager: new Radar Ping Sound property; MsgRadarPing now goes to
all clients (spawnBlips flag keeps blips hunter-only), sound plays 3D
at each pinged hider. Distance-based stagger (speed of sound + 35 ms
min gap) prevents phase cancellation when multiple hiders ping.

SoundEffect: new spatialize toggle (per asset, applied only to 3D
instances -> Steam Audio HRTF); removed unused fade field.

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

Assets/Scripts/Audio/SoundEffectOptions.cs

@@ -20,13 +20,13 @@ namespace Prototype
         public Vector2? distanceRange;
         public Vector2 GetDistanceRange() => distanceRange ?? new(30, 200);
 
-        public Vector2? fade;
-        public Vector2 GetFade() => fade ?? new();
-
         public bool? destroyOnLoad;
         public bool ShouldDestroyOnLoad() => destroyOnLoad ?? true;
 
         public float? delay;
         public float GetDelay() => delay ?? 0;
+
+        public bool? spatialize;
+        public bool GetSpatialize() => spatialize ?? false;
     }
 }