feat: ajout favicon et icônes cross-platform (web, iOS, PWA)

- iconfull.png comme favicon browser, apple-touch-icon et icône PWA
- manifest.json pour support Android/PWA
- icon.svg clipboard cyan dans public/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/manifest.json

@@ -0,0 +1,17 @@
+{
+  "name": "Évaluateur Maturité IA Gen",
+  "short_name": "IAG Evaluator",
+  "description": "Outil d'évaluation de la maturité IA Gen par Peaksys",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#09090b",
+  "theme_color": "#06B6D4",
+  "icons": [
+    {
+      "src": "/iconfull.png",
+      "sizes": "any",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ]
+}