feat: implement pure JavaScript image watermarking with sharp (no Python)

package.json

@@ -19,6 +19,7 @@
     "qrcode.react": "^4.2.0",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
+    "sharp": "^0.35.5",
     "tailwind-merge": "^3.6.0"
   },
   "devDependencies": {
@@ -26,6 +27,7 @@
     "@types/node": "^26.5.0",
     "@types/react": "^18.3.12",
     "@types/react-dom": "^18.3.1",
+    "@types/sharp": "^0.31.1",
     "autoprefixer": "^10.5.5",
     "postcss": "^8.5.28",
     "tailwindcss": "^3.4.14",