desktop notifications don't have the proper app name or desktop entry

here's how [mako](https://wayland.emersion.fr/mako/) sees the supersonic notifications:

```json
{
"type": "aa{sv}",
"data": [
[
{
"app-name": {
"type": "s",
"data": "missing-id-1736792973"
},
"app-icon": {
"type": "s",
"data": "/home/anarcat/.var/app/io.github.dweymouth.supersonic/cache/fyne/missing-id-1736792973/icon.png"
},
"category": {
"type": "s",
"data": ""
},
"desktop-entry": {
"type": "s",
"data": ""
},
"summary": {
"type": "s",
"data": "Tfou 3lik"
},
"body": {
"type": "s",
"data": " – Taqbir"
},
"id": {
"type": "u",
"data": 1
},
"urgency": {
"type": "y",
"data": 255
},
"actions": {
"type": "a{ss}",
"data": {}
}
}
]
]
}
```

note the important bits:

```json
"app-name": {
"type": "s",
"data": "missing-id-1736792973"
},
"app-icon": {
"type": "s",
"data": "/home/anarcat/.var/app/io.github.dweymouth.supersonic/cache/fyne/missing-id-1736792973/icon.png"
},
"category": {
"type": "s",
"data": ""
},
"desktop-entry": {
"type": "s",
"data": ""
},
```

... are somewhat blank, which makes it hard to filter those notifications. amazingly, the `app-icon` field is there, but the others are not...

@dweymouth does that sound familiar? i am thinking this could be another flatpak issue, but looking at the path to the `app-icon` file (which has `cache/fyne` in it) makes me think this might be a fyne issue as well...

The issue names no files, tests, or entry points. Start by tracing where Supersonic creates desktop notifications and inspect how Fyne supplies the app name, icon, and desktop-entry fields. Done means the notification data contains the proper application name and desktop entry instead of blank or generated values, with filtering working in mako.

Written by the indexing model from the issue text.