feat: scaffold Tauri + Svelte client

SvelteKit in SPA mode with Tauri v2. Builds and produces .deb bundle.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src-tauri/src/main.rs

@@ -0,0 +1,6 @@
+// Prevents additional console window on Windows in release, DO NOT REMOVE!!
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
+fn main() {
+    client_lib::run()
+}