feat(v2): retours cand0o — nav, configs génériques, bloc Ambition

- Nav: fix layout (logo shrink-0, menu xl: only, whitespace-nowrap partout).
- Configurations: retire prix et specs techniques, ne garde que les features
  génériques par cible (hydrophone, capteurs physico-chimiques, autonomie
  énergie, transmission sans fil, ancrage renforcé pour EOLIEN).
- Ambition: nouveau composant 'Du ponctuel au grand réseau côtier' + entrée
  dans la nav, entre Concept et Pourquoi.

src/components/Nav.astro

@@ -2,6 +2,7 @@
 const base = import.meta.env.BASE_URL;
 const items = [
   { href: '#concept', label: 'Concept' },
+  { href: '#ambition', label: 'Ambition' },
   { href: '#pourquoi', label: 'Pourquoi' },
   { href: '#configurations', label: 'Configurations' },
   { href: '#architecture', label: 'Architecture' },
@@ -13,8 +14,8 @@ const items = [
 ---
 
 <header class="sticky top-0 z-40 border-b border-white/5 bg-abyss-950/75 backdrop-blur">
-  <div class="container-narrow flex h-16 items-center justify-between">
-    <a href={base} class="flex items-center gap-2.5" aria-label="NowYouSea — retour à l'accueil">
+  <div class="container-narrow flex h-16 items-center gap-6">
+    <a href={base} class="flex shrink-0 items-center gap-2.5" aria-label="NowYouSea — retour à l'accueil">
       <span class="relative inline-flex h-8 w-8 items-center justify-center rounded-md bg-gradient-to-br from-tide-500 to-lagoon-500 shadow-glow">
         <svg viewBox="0 0 24 24" class="h-5 w-5 text-abyss-950" fill="currentColor" aria-hidden="true">
           <path d="M2 16c2 0 2-2 4-2s2 2 4 2 2-2 4-2 2 2 4 2 2-2 4-2v4H2z"/>
@@ -22,24 +23,26 @@ const items = [
           <path d="M7 9a5 5 0 0 1 10 0" stroke="currentColor" stroke-width="1.5" fill="none" opacity=".65"/>
         </svg>
       </span>
-      <span class="font-display text-base font-semibold tracking-tight">NowYouSea</span>
+      <span class="font-display text-base font-semibold tracking-tight whitespace-nowrap">NowYouSea</span>
     </a>
 
-    <nav aria-label="Navigation principale" class="hidden lg:block">
-      <ul class="flex items-center gap-7 text-sm text-foam-100/75">
+    <nav aria-label="Navigation principale" class="hidden flex-1 justify-center xl:flex">
+      <ul class="flex items-center gap-5 text-sm text-foam-100/75">
         {items.map((item) => (
           <li>
-            <a href={item.href} class="hover:text-tide-400">{item.label}</a>
+            <a href={item.href} class="whitespace-nowrap hover:text-tide-400">{item.label}</a>
           </li>
         ))}
       </ul>
     </nav>
 
-    <a href="#contact" class="btn btn-primary hidden md:inline-flex">
-      Demander une démo
-      <svg viewBox="0 0 24 24" class="h-4 w-4" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
-        <path d="M5 12h14M13 5l7 7-7 7"/>
-      </svg>
-    </a>
+    <div class="ml-auto shrink-0 xl:ml-0">
+      <a href="#contact" class="btn btn-primary hidden whitespace-nowrap md:inline-flex">
+        Demander une démo
+        <svg viewBox="0 0 24 24" class="h-4 w-4" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true">
+          <path d="M5 12h14M13 5l7 7-7 7"/>
+        </svg>
+      </a>
+    </div>
   </div>
 </header>