fix(desktop): enable window dragging on login page

Add WebkitAppRegion drag to login page background areas so the window
can be dragged on macOS. Mark the sign-in button as no-drag to keep it
clickable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/desktop/src/renderer/src/pages/login.tsx

@@ -23,14 +23,20 @@ export default function LoginPage() {
 
   if (isLoading) {
     return (
-      <div className="flex h-screen items-center justify-center bg-background">
+      <div
+        className="flex h-screen items-center justify-center bg-background"
+        style={{ WebkitAppRegion: 'drag' } as React.CSSProperties}
+      >
         <Loading className="size-6" />
       </div>
     )
   }
 
   return (
-    <div className="flex h-screen flex-col items-center justify-center bg-background p-8 animate-in fade-in duration-300">
+    <div
+      className="flex h-screen flex-col items-center justify-center bg-background p-8 animate-in fade-in duration-300"
+      style={{ WebkitAppRegion: 'drag' } as React.CSSProperties}
+    >
       <div className="w-full max-w-sm flex flex-col items-center text-center space-y-6">
         {/* Brand */}
         <div className="flex items-center gap-2">
@@ -44,7 +50,12 @@ export default function LoginPage() {
         </p>
 
         {/* Sign In */}
-        <Button onClick={startLogin} size="lg" className="px-8">
+        <Button
+          onClick={startLogin}
+          size="lg"
+          className="px-8"
+          style={{ WebkitAppRegion: 'no-drag' } as React.CSSProperties}
+        >
           Sign In to Continue
         </Button>