fix: add app icons and capabilities for Tauri v2 build

tauri-app/src-tauri/capabilities/default.json

@@ -0,0 +1,10 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Default capabilities for ForgeLM Chat",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "shell:allow-open"
+  ]
+}