physics: apply server walk and swim speed overrides to CameraController

serverWalkSpeed_ and serverSwimSpeed_ were stored in GameHandler but
never exposed or synced to the camera controller. The controller used
hardcoded WOW_WALK_SPEED and speed*SWIM_SPEED_FACTOR regardless of
server-sent speed changes.

Add getServerWalkSpeed()/getServerSwimSpeed() accessors, walkSpeedOverride_
and swimSpeedOverride_ fields in CameraController, and sync all three
server speeds each frame. Both swim speed sites (main and camera-collision
path) now use the override when set. This makes Slow debuffs (walk speed),
Swim Form, and Engineering fins actually affect movement speed.

src/core/application.cpp

@@ -1009,6 +1009,8 @@ void Application::update(float deltaTime) {
             runInGameStage("post-update sync", [&] {
                 if (renderer && gameHandler && renderer->getCameraController()) {
                     renderer->getCameraController()->setRunSpeedOverride(gameHandler->getServerRunSpeed());
+                    renderer->getCameraController()->setWalkSpeedOverride(gameHandler->getServerWalkSpeed());
+                    renderer->getCameraController()->setSwimSpeedOverride(gameHandler->getServerSwimSpeed());
                     renderer->getCameraController()->setMovementRooted(gameHandler->isPlayerRooted());
                     renderer->getCameraController()->setGravityDisabled(gameHandler->isGravityDisabled());
                 }