Add unlit rendering for M2 glow/additive batches

Batches with the M2 unlit material flag (0x01) or additive blend modes
(3+) now skip lighting, shadows, and fog, emitting texture color directly.
Fixes lantern glow quads appearing as dull transparent circles.

include/rendering/m2_renderer.hpp

@@ -33,6 +33,7 @@ struct M2ModelGPU {
         bool hasAlpha = false;
         uint16_t textureAnimIndex = 0xFFFF; // 0xFFFF = no texture animation
         uint16_t blendMode = 0;   // 0=Opaque, 1=AlphaKey, 2=Alpha, 3=Add, etc.
+        uint16_t materialFlags = 0; // M2 material flags (0x01=Unlit, 0x04=TwoSided, 0x10=NoDepthWrite)
     };
 
     GLuint vao = 0;

src/rendering/m2_renderer.cpp

@@ -261,6 +261,7 @@ bool M2Renderer::initialize(pipeline::AssetManager* assets) {
         uniform sampler2D uTexture;
         uniform bool uHasTexture;
         uniform bool uAlphaTest;
+        uniform bool uUnlit;
         uniform float uFadeAlpha;
 
         uniform vec3 uFogColor;
@@ -293,6 +294,12 @@ bool M2Renderer::initialize(pipeline::AssetManager* assets) {
                 discard;
             }
 
+            // Unlit path: emit texture color directly (glow effects, emissive surfaces)
+            if (uUnlit) {
+                FragColor = vec4(texColor.rgb, finalAlpha);
+                return;
+            }
+
             vec3 normal = normalize(Normal);
             vec3 lightDir = normalize(uLightDir);
 
@@ -729,9 +736,10 @@ bool M2Renderer::loadModel(const pipeline::M2Model& model, uint32_t modelId) {
                 gpuModel.hasTextureAnimation = true;
             }
 
-            // Store blend mode from material
+            // Store blend mode and flags from material
             if (batch.materialIndex < model.materials.size()) {
                 bgpu.blendMode = model.materials[batch.materialIndex].blendMode;
+                bgpu.materialFlags = model.materials[batch.materialIndex].flags;
             }
 
             // Resolve texture: batch.textureIndex → textureLookup → allTextures
@@ -1298,6 +1306,10 @@ void M2Renderer::render(const Camera& camera, const glm::mat4& view, const glm::
                 glDepthMask(GL_FALSE);
             }
 
+            // Unlit: material flag 0x01 or additive/mod blend modes
+            bool unlit = (batch.materialFlags & 0x01) != 0 || batch.blendMode >= 3;
+            shader->setUniform("uUnlit", unlit);
+
             bool hasTexture = (batch.texture != 0);
             shader->setUniform("uHasTexture", hasTexture);
             shader->setUniform("uAlphaTest", batch.blendMode == 1);