feat: minification serveur à la volée (terser + fallback Bun) et cache immutable

- import terser/Bun.Transpiler (fallback si terser indisponible)
- minifySrc(): CSS via regex, JS via terser.minify (compress+mangle) sinon source
- buildFileCache asynchrone, etag stable sha1(content), cache de minification hashé
- Cache-Control: html no-store, assets ?v= immutable 1 an, sinon must-revalidate

package.json

@@ -17,6 +17,7 @@
   "dependencies": {
     "marked": "^18.0.9",
     "sharp": "^0.35.3",
+    "terser": "^5.51.2",
     "wordpress-honeypot": "^1.1.2"
   }
 }