Improve buffer safety in body list string construction

Use snprintf with offset tracking instead of strcat to prevent
potential buffer overflow when building body list string for raygui.

src/renderer.cpp

@@ -377,16 +377,18 @@ void render_body_list_ui(SimulationState* sim, RenderState* render_state) {
     Rectangle panel_bounds = { (float)panel_x, (float)panel_y, (float)panel_width, (float)panel_height };
 
     // Create body list string for raygui (NULL-terminated)
-    char* body_list_text = (char*)malloc(sim->body_count * 64); // 64 chars per name max
+    int buffer_size = sim->body_count * (64 + 1) + 1;
+    char* body_list_text = (char*)malloc(buffer_size);
     if (!body_list_text) return;
 
-    body_list_text[0] = '\0'; // Initialize empty string
+    body_list_text[0] = '\0';
+    int offset = 0;
 
     for (int i = 0; i < sim->body_count; i++) {
         if (i > 0) {
-            strcat(body_list_text, ";"); // Separator for raygui
+            offset += snprintf(body_list_text + offset, buffer_size - offset, ";");
         }
-        strcat(body_list_text, sim->bodies[i].name);
+        offset += snprintf(body_list_text + offset, buffer_size - offset, "%s", sim->bodies[i].name);
     }
 
     // Draw window