feat: Adds robust speed hack detection and movement throttling (#2266)

## Summary

   Server-side movement throttle that prevents speed hacking while accurately identifying cheaters with detection of lagging connections.

   **Key features:**
   - Credit buffer (200ms) absorbs timing jitter from legitimate players
   - Movement queue handles larger bursts, draining at proper game-tick intervals
   - RTT measurement distinguishes network lag from speed hacks
   - Queue depth detection catches ACK-throttled speed hacks (going straight)

   ## How It Works

   **Throttle** (prevention): Movements arriving too early either consume credit or get queued. The queue drains at
   correct intervals, so speed hackers can't move faster regardless of what they send.

   **Detection** (identification): Combines multiple signals to identify cheaters:
   | Signal | What it catches |
   |--------|-----------------|
   | Queue depth ≥4 sustained | ACK-throttled speed hacks (client limits unacked moves to 5) |
   | Movement rate >1.05x | Direction-change speed hacks where timing is visible |
   | Stable RTT + high queue | Eliminates false positives from laggy players |

   **RTT-Aware Logic:**
   - Probes only sent to players actively moving (event-driven, not global loop)
   - Stable low-latency + problems = suspicious
   - Unstable/high-latency + problems = probably just lag, throttle handles it

   ## Configuration

   ```json
   {
     "movementThrottle.maxCredit": 200,
     "movementThrottle.softQueueLimit": 6,
     "movementThrottle.hardQueueLimit": 10,
     "movementThrottle.debugLogging": false
   }
   ```

Projects/UOContent/Network/Packets/IncomingAccountPackets.cs

@@ -194,6 +194,9 @@ public static class IncomingAccountPackets
     {
         var version = state.Version = new ClientVersion(reader.ReadAscii());
 
+        // Record RTT if this is a response to our probe
+        state.RecordRttMeasurement();
+
         ClientVerification.ClientVersionReceived(state, version);
     }
 
@@ -204,6 +207,9 @@ public static class IncomingAccountPackets
         int type = reader.ReadUInt16();
         var version = state.Version = new ClientVersion(reader.ReadAscii());
 
+        // Record RTT if this is a response to our probe
+        state.RecordRttMeasurement();
+
         ClientVerification.ClientVersionReceived(state, version);
     }
 
@@ -270,7 +276,7 @@ public static class IncomingAccountPackets
 
         state.SendSupportedFeature();
 
-        state.Sequence = 0;
+        state.ResetMovementState();
 
         state.SendMobileUpdate(m);
         state.SendMobileUpdate(m);

Projects/UOContent/Network/Packets/IncomingMovementPackets.cs

@@ -91,23 +91,9 @@ public static class IncomingMovementPackets
 
         var dir = (Direction)reader.ReadByte();
         int seq = reader.ReadByte();
-        var key = reader.ReadUInt32();
+        var key = reader.ReadUInt32(); // FastWalkStack key - not used (not on EA servers)
 
-        if (state.Sequence == 0 && seq != 0 || !from.Move(dir))
-        {
-            state.SendMovementRej(seq, from);
-            state.Sequence = 0;
-        }
-        else
-        {
-            ++seq;
-
-            if (seq == 256)
-            {
-                seq = 1;
-            }
-
-            state.Sequence = seq;
-        }
+        // Delegate to MovementThrottle which has full context for timing validation
+        MovementThrottle.ValidateAndQueueMovement(state, from, dir, seq);
     }
 }

Projects/UOContent/Network/Packets/IncomingPlayerPackets.cs

@@ -360,7 +360,7 @@ public static class IncomingPlayerPackets
 
         from.SendEverything();
 
-        state.Sequence = 0;
+        state.ResetMovementState();
     }
 
     public static void PingReq(NetState state, SpanReader reader)