Added Oxibadge, a minimal Tauri + Svelte desktop client

Scaffolds the oxibadge crate/frontend as a new workspace member, stripped
down to a bare hello-world, and
extends the CI pipeline

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

oxibadge/src-tauri/src/lib.rs

@@ -0,0 +1,6 @@
+#[cfg_attr(mobile, tauri::mobile_entry_point)]
+pub fn run() {
+    tauri::Builder::default()
+        .run(tauri::generate_context!())
+        .expect("error while running tauri application");
+}

oxibadge/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() {
+    oxibadge_lib::run()
+}