feat(tauri-app): Tauri 2 capabilities default + open_devtools in debug

The dev build was missing a capabilities/default.json so the
event:listen and notification:is-permission-granted plugins
denied every IPC call from main.ts (logged as 'event.listen not
allowed' etc. in DevTools). Add the minimum set needed by
client.ts / main.ts and the AppView/Tauri commands registered
in lib.rs.

Also open the webview devtools automatically on startup behind
a debug_assertions guard, so the frontend console + DOM inspector
are available without reaching for the macOS View menu.

crates/tauri-app/src-tauri/tauri.conf.json

@@ -28,7 +28,8 @@
       }
     ],
     "security": {
-      "csp": "default-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; connect-src 'self' ipc: http://ipc.localhost"
+      "csp": "default-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; connect-src 'self' ipc: http://ipc.localhost",
+      "capabilities": ["default"]
     }
   },
   "plugins": {