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/capabilities/default.json

@@ -0,0 +1,9 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Capability for the main window",
+  "windows": ["main"],
+  "permissions": [
+    "core:default"
+  ]
+}