feat(pc2): hamburger nav + manifeste V1 + popup onboarding

- HamburgerMenu drawer slide-in left avec liens A propos, Manifeste, Mentions legales (ESC + clic overlay pour fermer)
- ColJournal enrichi : CTA Manifeste, accordeon Hashtags (7 plateformes, ferme mobile / ouvert desktop, persistence localStorage), skeleton Journal pour PC6
- Page /manifeste : V1 redige integre (em-dashes remplaces par tirets/points-virgules), pivot stylise blockquote, diagramme mouvements en 3 sections boites
- Page /manifeste/commander : stub form pre-inscription (V1 localStorage, V1.1 cable Listmonk)
- Page /a-propos : extrait de Contexte Global, 3-4 paragraphes Jules
- Page /mentions-legales : placeholder court (editeur, hebergeur Hetzner, pas de cookies)
- PopupOnboarding : micro-resume 3 lignes proposees, dismiss X / CTA / scroll 200px / ESC, flag tf-onboarded

src/components/astro/PopupOnboarding.astro

@@ -1,11 +1,101 @@
 ---
-// Placeholder popup onboarding — PC2 fait l'animation et le contenu
+// PopupOnboarding - micro-resume premier visit, localStorage flag tf-onboarded
+// Le micro-resume est une PROPOSITION Opus a iterer avec Jules.
+// Stocke en constante en tete pour iteration facile.
+const microResume = `Architecture, ecologie, politique : un commun a construire ensemble.
+Reapproprions-nous nos infrastructures vitales en repartant de l'existant.
+Ce site, c'est le journal vivant de cette bifurcation.`;
 ---
 <div
-  id="pc-onboarding"
-  class="hidden fixed inset-0 z-40 bg-black/30 items-center justify-center"
+  id="onboarding-popup"
+  class="fixed inset-0 z-[60] hidden bg-black/50 backdrop-blur-sm items-center justify-center p-4"
+  role="dialog"
+  aria-modal="true"
+  aria-labelledby="onboarding-text"
 >
-  <div class="bg-white p-6 rounded shadow-lg max-w-sm">
-    <p class="text-sm text-neutral-600">Pop-up onboarding — PC2</p>
+  <div class="bg-white rounded-xl max-w-md w-full p-6 md:p-7 shadow-2xl relative animate-fade-in">
+    <button
+      id="onboarding-close"
+      type="button"
+      class="absolute top-3 right-3 w-8 h-8 flex items-center justify-center text-neutral-400 hover:text-neutral-800 text-2xl leading-none rounded-md hover:bg-neutral-100 transition-colors"
+      aria-label="Fermer"
+    >
+      &times;
+    </button>
+    <p
+      id="onboarding-text"
+      class="text-base md:text-lg leading-relaxed text-neutral-800 whitespace-pre-line pr-6"
+    >{microResume}</p>
+    <button
+      id="onboarding-cta"
+      type="button"
+      class="mt-5 px-4 py-2.5 bg-neutral-900 text-white rounded-lg w-full font-medium hover:bg-neutral-700 transition-colors"
+    >
+      Entrer
+    </button>
   </div>
 </div>
+
+<style>
+  @keyframes fadeIn {
+    from { opacity: 0; transform: translateY(8px); }
+    to   { opacity: 1; transform: translateY(0); }
+  }
+  .animate-fade-in {
+    animation: fadeIn 0.25s ease-out;
+  }
+</style>
+
+<script>
+  const STORAGE_KEY = 'tf-onboarded';
+  const popup = document.getElementById('onboarding-popup');
+  const closeBtn = document.getElementById('onboarding-close');
+  const ctaBtn = document.getElementById('onboarding-cta');
+
+  let alreadyOnboarded = false;
+  try {
+    alreadyOnboarded = !!localStorage.getItem(STORAGE_KEY);
+  } catch {
+    // mode prive : on affiche quand meme, sans persistence
+    alreadyOnboarded = false;
+  }
+
+  if (!alreadyOnboarded && popup) {
+    requestAnimationFrame(() => {
+      popup.classList.remove('hidden');
+      popup.classList.add('flex');
+    });
+  }
+
+  const dismiss = () => {
+    if (!popup) return;
+    popup.classList.remove('flex');
+    popup.classList.add('hidden');
+    try {
+      localStorage.setItem(STORAGE_KEY, '1');
+    } catch {
+      // mode prive : pas de persistence
+    }
+    window.removeEventListener('scroll', onScroll);
+  };
+
+  closeBtn?.addEventListener('click', dismiss);
+  ctaBtn?.addEventListener('click', dismiss);
+
+  // Dismiss implicite au scroll 200px (engagement implicite)
+  const onScroll = () => {
+    if (window.scrollY > 200) {
+      dismiss();
+    }
+  };
+  if (!alreadyOnboarded) {
+    window.addEventListener('scroll', onScroll, { passive: true });
+  }
+
+  // ESC pour fermer
+  document.addEventListener('keydown', (e) => {
+    if (e.key === 'Escape' && popup && !popup.classList.contains('hidden')) {
+      dismiss();
+    }
+  });
+</script>