Fix sun quad visibility, minimap opacity, audio scaling, and rename music toggle

- Tighten celestial glow falloff and edge fade to eliminate visible quad boundary
- Add opacity support to minimap display shader, synced with UI opacity setting
- Fix audio double/triple-scaling by removing redundant master volume multiplications
- Rename "Original Soundtrack" toggle to "Enable WoWee Music"
- Add About tab with developer info and GitHub link

assets/shaders/minimap_display.frag.glsl

@@ -9,6 +9,7 @@ layout(push_constant) uniform Push {
     float arrowRotation;
     float zoomRadius;
     int squareShape;
+    float opacity;
 } push;
 
 layout(location = 0) in vec2 TexCoord;
@@ -63,5 +64,5 @@ void main() {
         mapColor.rgb *= 1.0 - border * 0.7;
     }
 
-    outColor = mapColor;
+    outColor = vec4(mapColor.rgb, mapColor.a * push.opacity);
 }