fix(desktop): give the window a real title and a usable default size

tauri.conf.json still carried the scaffold defaults: a lowercase "jellytau"
title in an 800x600 window. The title is what the OS shows in the task
switcher and window list, and 800x600 is too small for a media library grid
with a mini player docked at the bottom.

Now "JellyTau" at 1280x800, with minWidth/minHeight held at the old 800x600
so the layout still has a defined floor when a user drags the window small.

src-tauri/tauri.conf.json

@@ -12,9 +12,12 @@
   "app": {
     "windows": [
       {
-        "title": "jellytau",
-        "width": 800,
-        "height": 600
+        "title": "JellyTau",
+        "width": 1280,
+        "height": 800,
+        "minWidth": 800,
+        "minHeight": 600,
+        "resizable": true
       }
     ],
     "security": {