Performance optimizations and collision improvements

Performance:
- Remove expensive inverse() from all vertex shaders (terrain, WMO, M2, water, character)
- Add uniform location caching to avoid repeated glGetUniformLocation calls
- Add proper frustum culling for WMO groups using AABB intersection
- Add distance-based culling for WMO and M2 instances
- Add cleanup of unused M2/WMO models when tiles unload

Collision & Movement:
- Add M2 doodad collision detection (fences, boxes, etc.)
- Reduce character eye height (5.0 -> 1.8) and collision radius (2.5 -> 0.5)
- Enable WoW-style movement speed by default (14 units/sec run, 5 walk, 9 back)
- Fix emote grammar ("You waves." -> "You wave.")

Misc:
- Rename window title to "Wowee"

assets/shaders/basic.vert

@@ -14,7 +14,8 @@ uniform mat4 uProjection;
 
 void main() {
     FragPos = vec3(uModel * vec4(aPosition, 1.0));
-    Normal = mat3(transpose(inverse(uModel))) * aNormal;
+    // Use mat3(uModel) directly - avoids expensive inverse() per vertex
+    Normal = mat3(uModel) * aNormal;
     TexCoord = aTexCoord;
 
     gl_Position = uProjection * uView * vec4(FragPos, 1.0);

assets/shaders/terrain.vert

@@ -18,8 +18,8 @@ void main() {
     vec4 worldPos = uModel * vec4(aPosition, 1.0);
     FragPos = worldPos.xyz;
 
-    // Transform normal to world space
-    Normal = mat3(transpose(inverse(uModel))) * aNormal;
+    // Terrain uses identity model matrix, so normal passes through directly
+    Normal = aNormal;
 
     TexCoord = aTexCoord;
     LayerUV = aLayerUV;