feat(ui): polish command palette and login page for Deep Space

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

frontend/src/components/command-palette/CommandPalette.tsx

@@ -216,7 +216,7 @@ export function CommandPalette() {
       overlayClassName="fixed inset-0 z-50 bg-background/80 backdrop-blur-sm"
       contentClassName="fixed left-1/2 top-[20%] -translate-x-1/2 z-50 w-full max-w-lg"
     >
-      <div className="rounded-xl border border-border bg-surface shadow-2xl overflow-hidden">
+      <div className="rounded-lg border border-border bg-surface overflow-hidden">
         <div className="flex items-center gap-2 px-4 border-b border-border">
           <Search className="h-4 w-4 text-text-muted flex-shrink-0" />
           <Command.Input

frontend/src/routes/login.tsx

@@ -125,7 +125,7 @@ function LoginPage() {
         </div>
 
         {/* Login card */}
-        <div className="rounded-lg border border-border bg-surface/50 p-6">
+        <div className="rounded-lg border border-border bg-surface p-6">
           <form onSubmit={(e) => void handleSubmit(e)} className="space-y-4">
             <div className="space-y-1.5">
               <Label htmlFor="email">Email</Label>
@@ -215,6 +215,7 @@ function LoginPage() {
 
             <Button
               type="submit"
+              variant="solid"
               className="w-full"
               data-testid="button-sign-in"
               disabled={