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/Server.Tests/Tests/Network/Packets/Outgoing/VendorSellPackets.cs

@@ -1,18 +1,3 @@
-/*************************************************************************
- * ModernUO                                                              *
- * Copyright 2019-2026 - ModernUO Development Team                       *
- * Email: hi@modernuo.com                                                *
- * File: VendorSellPackets.cs                                            *
- *                                                                       *
- * This program is free software: you can redistribute it and/or modify  *
- * it under the terms of the GNU General Public License as published by  *
- * the Free Software Foundation, either version 3 of the License, or     *
- * (at your option) any later version.                                   *
- *                                                                       *
- * You should have received a copy of the GNU General Public License     *
- * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
- *************************************************************************/
-
 using System.Collections.Generic;
 
 namespace Server.Network;