fix(shader): Use custom_background callback to render blurred texture

- Add _render_custom_background method as hello_imgui callback
- Render blurred FBO texture as ImGui background
- Use ctypes.cast to convert OpenGL texture ID to ImTextureRef

conductor/tracks.md

@@ -82,8 +82,9 @@ This file tracks all major tracks for the project. Each track has its own detail
 11. [ ] **Track: Advanced Text Viewer with Syntax Highlighting**
     *Link: [./tracks/text_viewer_rich_rendering_20260313/](./tracks/text_viewer_rich_rendering_20260313/)*
 
-12. [ ] **Track: Frosted Glass Background Effect**
+12. [ ] ~~**Track: Frosted Glass Background Effect**~~ THIS IS A LOST CAUSE DON'T BOTHER.
     *Link: [./tracks/frosted_glass_20260313/](./tracks/frosted_glass_20260313/)*
+    
 
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