Enhanced sky atmosphere with DBC-driven colors, sun lighting, and zone weather

- Skybox now uses DBC sky colors (skyTop/skyMiddle/skyBand1/skyBand2) instead
  of hardcoded C++ color curves, with 3-band gradient and Rayleigh/Mie scattering
- Clouds receive sun direction for lit edges, self-shadowing, and silver lining
- Fixed sun quad box artifact with proper edge fade in celestial shader
- Lens flare attenuated by fog, cloud density, and weather intensity
- Replaced garish green/purple lens flare ghosts with warm natural palette
- Added zone-based weather system for single-player mode with per-zone rain/snow
  configuration, probability-based activation, and smooth intensity transitions
- Server SMSG_WEATHER remains authoritative when connected to a server

src/rendering/sky_system.cpp

@@ -105,9 +105,9 @@ void SkySystem::render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet,
         return;
     }
 
-    // --- Skybox (authoritative sky gradient) ---
+    // --- Skybox (authoritative sky gradient, DBC-driven colors) ---
     if (skybox_) {
-        skybox_->render(cmd, perFrameSet, params.timeOfDay);
+        skybox_->render(cmd, perFrameSet, params);
     }
 
     // --- Procedural stars (debug / fallback) ---
@@ -133,15 +133,17 @@ void SkySystem::render(VkCommandBuffer cmd, VkDescriptorSet perFrameSet,
                            &params.directionalDir, &params.sunColor, params.gameTime);
     }
 
-    // --- Clouds ---
+    // --- Clouds (DBC-driven colors + sun lighting) ---
     if (clouds_) {
-        clouds_->render(cmd, perFrameSet, params.timeOfDay);
+        clouds_->render(cmd, perFrameSet, params);
     }
 
-    // --- Lens flare ---
+    // --- Lens flare (attenuated by atmosphere) ---
     if (lensFlare_) {
         glm::vec3 sunPos = getSunPosition(params);
-        lensFlare_->render(cmd, camera, sunPos, params.timeOfDay);
+        lensFlare_->render(cmd, camera, sunPos, params.timeOfDay,
+                           params.fogDensity, params.cloudDensity,
+                           params.weatherIntensity);
     }
 }