feat(wm): add theme socket message

This commit adds a new SocketMessage::Theme which allows for themes to
be set programmatically. This change has also been plumbed through to
komorebi-bar so that the bar theme will also update after komorebi
processes the message and passes it on to subscribers.

A new theme_manager module has been introduced to add notification-based
handling of theme changes, both from the static config file being
updated and from SocketMessage::Theme being received.

justfile

@@ -26,17 +26,17 @@ install:
 run target:
     cargo +stable run --bin {{ target }} --locked
 
-warn $RUST_LOG="warn":
-    just run
+warn target $RUST_LOG="warn":
+    just run {{ target }}
 
-info $RUST_LOG="info":
-    just run
+info target $RUST_LOG="info":
+    just run {{ target }}
 
-debug $RUST_LOG="debug":
-    just run
+debug target $RUST_LOG="debug":
+    just run {{ target }}
 
-trace $RUST_LOG="trace":
-    just run
+trace target $RUST_LOG="trace":
+    just run {{ target }}
 
 deadlock $RUST_LOG="trace":
     cargo +stable run --bin komorebi --locked --features deadlock_detection