physics: block client-side movement when server roots the player

When SMSG_FORCE_MOVE_ROOT sets ROOT in movementInfo.flags, the
camera controller was not aware and continued to accept directional
input. This caused position desync (client moves, server sees player
as rooted).

- Add movementRooted_ flag to CameraController with setter/getter.
- Block nowForward/nowBackward/nowStrafe when movementRooted_ is set.
- Sync isPlayerRooted() from GameHandler to CameraController each
  frame alongside the existing run-speed sync in application.cpp.
- Add GameHandler::isPlayerRooted() convenience accessor.

src/rendering/camera_controller.cpp

@@ -275,8 +275,10 @@ void CameraController::update(float deltaTime) {
     if (mouseAutorun) {
         autoRunning = false;
     }
-    bool nowForward = keyW || mouseAutorun || autoRunning;
-    bool nowBackward = keyS;
+    // When the server has rooted the player, suppress all horizontal movement input.
+    const bool movBlocked = movementRooted_;
+    bool nowForward = !movBlocked && (keyW || mouseAutorun || autoRunning);
+    bool nowBackward = !movBlocked && keyS;
     bool nowStrafeLeft = false;
     bool nowStrafeRight = false;
     bool nowTurnLeft = false;