Add gamma control and night light (#38)

Add configurable night light, smooth gamma transitions, and shell controls. Update documentation and panel tests, and fix portal test startup synchronization.

crates/ferese-ipc/src/lib.rs

@@ -10,6 +10,7 @@ use serde_json::Value;
 
 pub mod events;
 pub mod media;
+pub mod night_light;
 pub mod socket;
 pub mod theme;
 pub mod xwayland;