refactor: decompose TransportManager and upgrade Entity to CatmullRom splines

TransportManager decomposition:
- Extract TransportClockSync: server clock offset, yaw flip detection,
  velocity bootstrap, client/server mode switching
- Extract TransportAnimator: spline evaluation, Z clamping, orientation
  from server yaw or spline tangent
- Slim TransportManager to thin orchestrator delegating to ClockSync and
  Animator; add pushTransform() helper to deduplicate WMO/M2 renderer calls
- Remove legacy orientationFromSplineTangent (now uses
  CatmullRomSpline::orientationFromTangent)

Entity path following upgrade:
- Replace pathPoints_/pathSegDists_ linear lerp with
  std::optional<CatmullRomSpline> activeSpline_
- startMoveAlongPath builds SplineKeys with distance-proportional timing
- updateMovement evaluates CatmullRomSpline for smooth Catmull-Rom
  interpolation matching server-side creature movement
- Reset activeSpline_ on setPosition/startMoveTo to prevent stale state

Tests:
- Add test_transport_components (9 cases): ClockSync client/server/reverse
  modes, yaw flip detection, Animator position eval, server yaw, Z clamping
- Link spline.cpp into test_entity for CatmullRomSpline dependency

Signed-off-by: Pavel Okhlopkov <pavel.okhlopkov@flant.com>

include/game/transport_manager.hpp

@@ -1,6 +1,8 @@
 #pragma once
 
 #include "game/transport_path_repository.hpp"
+#include "game/transport_clock_sync.hpp"
+#include "game/transport_animator.hpp"
 #include <cstdint>
 #include <vector>
 #include <unordered_map>
@@ -124,10 +126,11 @@ public:
 private:
     void updateTransportMovement(ActiveTransport& transport, float deltaTime);
     void updateTransformMatrices(ActiveTransport& transport);
-    /// Legacy transport orientation from tangent (preserves original cross-product order).
-    static glm::quat orientationFromSplineTangent(const glm::vec3& tangent);
+    void pushTransform(ActiveTransport& transport);
 
     TransportPathRepository pathRepo_;
+    TransportClockSync clockSync_;
+    TransportAnimator animator_;
     std::unordered_map<uint64_t, ActiveTransport> transports_;
     rendering::WMORenderer* wmoRenderer_ = nullptr;
     rendering::M2Renderer* m2Renderer_ = nullptr;