feat: integrate WebP/AVIF image optimization into build pipeline

- Add sharp dependency for image format conversion
- Generate WebP (quality 80) and AVIF (quality 70) variants for all raster images
- Render <picture> elements with srcset fallbacks (AVIF > WebP > original)
- SVG images remain as <img> without picture wrapper
- Update Dockerfile to install libvips for sharp, copy from public/ dir
- Add nginx cache rules for .webp and .avif files
- Add .gitignore for node_modules, public, dist

package.json

@@ -1,10 +1,16 @@
 {
   "name": "signalledger.nl",
   "version": "1.0.0",
-  "description": "Signal Ledger news site",
+  "private": true,
+  "type": "module",
   "scripts": {
-    "build": "node build.js",
-    "test": "node test.js"
+    "build": "node src/build.js",
+    "test": "node test.js",
+    "serve": "python3 -m http.server 8080 -d public"
   },
-  "devDependencies": {}
+  "dependencies": {
+    "openai": "^4.104.0",
+    "rss-parser": "^3.13.0",
+    "sharp": "^0.34.5"
+  }
 }