feat: nouveau favicon (globe aquarelle) — remplace le placeholder FX

app/icon.png + app/apple-icon.png (convention Next.js, auto-génère les
balises <link>), manifest.json PWA mis à jour vers les mêmes PNG.
Supprime les anciens SVG placeholder devenus orphelins.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

public/icons/icon-192.svg

@@ -1,4 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="192" height="192" viewBox="0 0 192 192">
-  <rect width="192" height="192" rx="34" fill="#090e1a"/>
-  <text x="50%" y="54%" font-family="Arial,sans-serif" font-weight="bold" font-size="80" fill="#f59e0b" text-anchor="middle" dominant-baseline="middle">FX</text>
-</svg>

public/icons/icon-512.svg

@@ -1,4 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="512" height="512" viewBox="0 0 512 512">
-  <rect width="512" height="512" rx="92" fill="#090e1a"/>
-  <text x="50%" y="54%" font-family="Arial,sans-serif" font-weight="bold" font-size="215" fill="#f59e0b" text-anchor="middle" dominant-baseline="middle">FX</text>
-</svg>

public/manifest.json

@@ -9,15 +9,15 @@
   "orientation": "portrait-primary",
   "icons": [
     {
-      "src": "/icons/icon-192.svg",
+      "src": "/icons/icon-192.png",
       "sizes": "192x192",
-      "type": "image/svg+xml",
+      "type": "image/png",
       "purpose": "any maskable"
     },
     {
-      "src": "/icons/icon-512.svg",
+      "src": "/icons/icon-512.png",
       "sizes": "512x512",
-      "type": "image/svg+xml",
+      "type": "image/png",
       "purpose": "any maskable"
     }
   ]