chore: upgrade to React 19 and use images.remotePatterns

Fixes Next.js 16 deprecation warnings for React 18 and images.domains.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

package.json

@@ -9,8 +9,8 @@
   },
   "dependencies": {
     "next": "^16.4.3",
-    "react": "^18.2.0",
-    "react-dom": "^18.2.0",
+    "react": "^19.3.1",
+    "react-dom": "^19.3.1",
     "sass": "^1.32.12"
   },
   "devDependencies": {