Enable HDR lighting with Reinhard tonemapping across all world shaders

Replace hardcoded specular multipliers with uLightColor * uSpecularIntensity
uniforms in all 4 world shaders (terrain, WMO, M2, character), set HDR sun
color (1.5, 1.4, 1.3) and specular intensity 0.5 so highlights can exceed
1.0, and switch the post-process pass from passthrough to exposure-compensated
Reinhard (exposure=1.8) for soft highlight roll-off without clipping.

src/rendering/renderer.cpp

@@ -1176,8 +1176,10 @@ void Renderer::initPostProcess(int w, int h) {
         out vec4 FragColor;
         void main() {
             vec3 color = texture(uScene, vUV).rgb;
-            // Passthrough — tonemap will kick in once HDR lighting is added
-            FragColor = vec4(color, 1.0);
+            float exposure = 1.8;
+            color *= exposure;
+            vec3 mapped = color / (color + vec3(1.0));
+            FragColor = vec4(mapped, 1.0);
         }
     )";
     postProcessShader = std::make_unique<Shader>();