Fix main-thread hang from terrain finalization; two-pass M2 rendering; tile streaming improvements

Hang/GPU device lost fix:
- M2_INSTANCES and WMO_INSTANCES finalization phases now create instances
  incrementally (32 per step / 4 per step) instead of all at once, eliminating
  the >1s main-thread stalls that caused GPU fence timeouts and device loss

M2 two-pass transparent rendering:
- Opaque/alpha-test batches render in pass 1, transparent/additive in pass 2
  (back-to-front sorted) to fix wing transparency showing terrain instead of
  trees — adds hasTransparentBatches flag to skip models with no transparency

Tile streaming improvements:
- Sort new load queue entries nearest-first so critical tiles load before
  distant ones during fast taxi flight
- Increase taxi load radius 6→8 tiles, unload 9→12 for better coverage

Water refraction gated on FSR:
- Disable water refraction when FSR is not active (bugged without upscaling)
- Auto-disable refraction if FSR is turned off while refraction was on

src/core/application.cpp

@@ -1108,8 +1108,8 @@ void Application::update(float deltaTime) {
                 // Taxi flights move fast (32 u/s) — load further ahead so terrain is ready
                 // before the camera arrives.  Keep updates frequent to spot new tiles early.
                 renderer->getTerrainManager()->setUpdateInterval(onTaxi ? 0.033f : 0.033f);
-                renderer->getTerrainManager()->setLoadRadius(onTaxi ? 6 : 4);
-                renderer->getTerrainManager()->setUnloadRadius(onTaxi ? 9 : 7);
+                renderer->getTerrainManager()->setLoadRadius(onTaxi ? 8 : 4);
+                renderer->getTerrainManager()->setUnloadRadius(onTaxi ? 12 : 7);
                 renderer->getTerrainManager()->setTaxiStreamingMode(onTaxi);
                 }
                 lastTaxiFlight_ = onTaxi;