Switch to opaque frameless window for cross-platform reliability

Transparent windows require platform-specific workarounds (WebView2 on
Windows, compositor support on Linux) and don't work on mobile. Use an
opaque window instead, removing the outer padding, rounded corners, and
drop shadow that depended on transparency.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/tauri/src-tauri/tauri.conf.json

@@ -20,7 +20,7 @@
         "minHeight": 500,
         "resizable": true,
         "decorations": false,
-        "transparent": true
+        "transparent": false
       }
     ],
     "security": {

apps/tauri/src/App.svelte

@@ -11,10 +11,10 @@
 </script>
 
 <div class={app.darkMode ? "dark" : ""}>
-  <div class="h-screen w-screen p-2">
+  <div class="h-screen w-screen">
     <div
-      class="relative h-full w-full overflow-hidden rounded-xl border border-black/15 bg-surface-light text-text-light dark:border-white/15 dark:bg-surface-dark dark:text-text-dark"
-      style="container-type: inline-size; box-shadow: 0 2px 8px rgba(0,0,0,0.25), 0 0 2px rgba(0,0,0,0.1)"
+      class="relative h-full w-full overflow-hidden bg-surface-light text-text-light dark:bg-surface-dark dark:text-text-dark"
+      style="container-type: inline-size"
     >
       {#if app.error}
         <div

apps/tauri/src/app.css

@@ -24,16 +24,11 @@
   -moz-osx-font-smoothing: grayscale;
 }
 
-html {
-  background: transparent;
-}
-
 body {
   margin: 0;
   overflow: hidden;
   user-select: none;
   -webkit-user-select: none;
-  background: transparent;
 }
 
 /* Scrollbar styling */