feat(auth): redesign auth pages with glass UI and motion animations

- error page: replace Card with glass-strong panel, add AlertTriangle icon
- signin page: add framer-motion entrance animation, CalendarDays branding,
  Loader2 spinner while loading, merge isPending/session checks
- signout page: replace Card with glass-strong panel, add LogOut icon,
  tighten user identity display

src/app/auth/signin/page.tsx

@@ -1,17 +1,12 @@
 "use client";
 
+import { motion } from "framer-motion";
+import { CalendarDays, Loader2 } from "lucide-react";
 import Link from "next/link";
 import { useRouter } from "next/navigation";
 import { useEffect, useState } from "react";
 import { toast } from "sonner";
 import { Button } from "@/components/ui/button";
-import {
-	Card,
-	CardContent,
-	CardDescription,
-	CardHeader,
-	CardTitle,
-} from "@/components/ui/card";
 import { signIn, useSession } from "@/lib/auth-client";
 
 export default function SignInPage() {
@@ -39,43 +34,46 @@ export default function SignInPage() {
 		}
 	};
 
-	if (isPending) {
-		return null;
-	}
-
-	if (session?.user) {
+	if (isPending || session?.user) {
 		return null;
 	}
 
 	return (
-		<div className="min-h-screen flex items-center justify-center bg-background p-4">
-			<Card className="w-full max-w-md">
-				<CardHeader className="text-center">
-					<CardTitle className="text-2xl font-bold">Welcome</CardTitle>
-					<CardDescription>
-						Sign in to access AI-powered calendar features
-					</CardDescription>
-				</CardHeader>
-				<CardContent className="space-y-4">
-					<Button
-						onClick={handleSignIn}
-						className="w-full"
-						size="lg"
-						disabled={isLoading}
-					>
-						{isLoading ? "Signing in..." : "Continue with Authentik"}
-					</Button>
+		<div className="min-h-screen flex items-center justify-center p-4">
+			<motion.div
+				initial={{ opacity: 0, y: 16 }}
+				animate={{ opacity: 1, y: 0 }}
+				transition={{ duration: 0.3 }}
+				className="glass-strong p-8 max-w-sm w-full text-center"
+			>
+				<div className="flex items-center justify-center gap-2 mb-6">
+					<CalendarDays className="h-6 w-6 text-primary" />
+					<h1 className="text-xl font-semibold tracking-tight">Local iCal</h1>
+				</div>
 
-					<div className="text-center">
-						<Link
-							href="/"
-							className="text-sm text-muted-foreground hover:underline"
-						>
-							Continue without signing in
-						</Link>
-					</div>
-				</CardContent>
-			</Card>
+				<p className="text-sm text-muted-foreground mb-6">
+					Sign in to unlock AI-powered event creation
+				</p>
+
+				<Button
+					onClick={handleSignIn}
+					className="w-full"
+					size="default"
+					disabled={isLoading}
+				>
+					{isLoading ? <Loader2 className="h-4 w-4 animate-spin mr-2" /> : null}
+					{isLoading ? "Signing in..." : "Continue with Authentik"}
+				</Button>
+
+				<div className="mt-4">
+					<Link
+						href="/"
+						className="text-xs text-muted-foreground hover:text-foreground transition-colors"
+					>
+						Continue without signing in
+					</Link>
+				</div>
+			</motion.div>
 		</div>
 	);
 }