feat: polish app loading screen and home section emphasis

Refine the global loading experience to feel smoother and less flashy while keeping brand accents. Simplify the home continue-reading highlight by styling the section header instead of using a heavy card wrapper.

src/app/loading.tsx

@@ -0,0 +1,44 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+const SHOW_DELAY_MS = 140;
+
+export default function AppLoading() {
+  const [isVisible, setIsVisible] = useState(false);
+
+  useEffect(() => {
+    const timeoutId = window.setTimeout(() => {
+      setIsVisible(true);
+    }, SHOW_DELAY_MS);
+
+    return () => window.clearTimeout(timeoutId);
+  }, []);
+
+  return (
+    <main
+      className={`flex min-h-screen items-center justify-center px-6 transition-opacity duration-300 motion-reduce:transition-none ${
+        isVisible ? "opacity-100" : "opacity-0"
+      }`}
+    >
+      <div className="flex w-full max-w-sm flex-col items-center gap-6 text-center">
+        <div className="space-y-2">
+          <p className="bg-gradient-to-r from-primary via-cyan-500 to-fuchsia-500 bg-clip-text text-xl font-bold uppercase tracking-[0.12em] text-transparent">
+            StripStream
+          </p>
+          <p className="text-sm text-muted-foreground">Chargement de votre bibliotheque...</p>
+        </div>
+
+        <div className="flex items-center gap-2" aria-hidden>
+          <span className="h-2 w-2 animate-bounce rounded-full bg-primary [animation-delay:-200ms]" />
+          <span className="h-2 w-2 animate-bounce rounded-full bg-cyan-500 [animation-delay:-100ms]" />
+          <span className="h-2 w-2 animate-bounce rounded-full bg-fuchsia-500" />
+        </div>
+
+        <div className="relative h-1.5 w-56 overflow-hidden rounded-full bg-muted/80" aria-hidden>
+          <div className="animate-loader-slide absolute inset-y-0 w-1/3 rounded-full bg-gradient-to-r from-primary via-cyan-500 to-fuchsia-500" />
+        </div>
+      </div>
+    </main>
+  );
+}