physics: sync all server movement speeds to CameraController

Previously only run speed was synced. Now all server-driven movement
speeds are forwarded to the camera controller each frame:
- runSpeedOverride_: server run speed (existing)
- walkSpeedOverride_: server walk speed (Ctrl key movement)
- swimSpeedOverride_: swim speed (Swim Form, Engineering fins)
- flightSpeedOverride_: flight speed (epic vs normal flying mounts)
- runBackSpeedOverride_: back-pedal speed

Each uses the server value when non-zero/sane, falling back to the
hardcoded WoW default constant otherwise.

src/core/application.cpp

@@ -1012,6 +1012,7 @@ void Application::update(float deltaTime) {
                     renderer->getCameraController()->setWalkSpeedOverride(gameHandler->getServerWalkSpeed());
                     renderer->getCameraController()->setSwimSpeedOverride(gameHandler->getServerSwimSpeed());
                     renderer->getCameraController()->setFlightSpeedOverride(gameHandler->getServerFlightSpeed());
+                    renderer->getCameraController()->setRunBackSpeedOverride(gameHandler->getServerRunBackSpeed());
                     renderer->getCameraController()->setMovementRooted(gameHandler->isPlayerRooted());
                     renderer->getCameraController()->setGravityDisabled(gameHandler->isGravityDisabled());
                     renderer->getCameraController()->setFeatherFallActive(gameHandler->isFeatherFalling());