feat: implement client backend

This includes temporary AI-generated frontend scaffolding, none of this will be used in production. It was just used during development for the backend.

build.rs

@@ -1,3 +1,6 @@
+use slint_build::CompilerConfiguration;
+
 fn main() {
-    slint_build::compile("ui/main.slint").expect("Failed to compile Slint UI");
-}
+    let config = CompilerConfiguration::new().with_style("fluent-dark".to_owned());
+    slint_build::compile_with_config("ui/main.slint", config).expect("Failed to compile Slint UI");
+}