PHP dynamique + cache JSON, nettoyage CSS/HTML, CI Forgejo

- Renommage classes/IDs (BEM cohérent, anglais, noms sémantiques)
- Correction HTML : h3→h2 FAQ, button>a→a[role=button] CTA mobile
- Conversion index.html → index.php (FR/EN) avec cache JSON depuis API Kirby
- Pages merci/thanks converties en PHP dynamique
- Ajout includes/cache.php + includes/config.php (cache TTL 5min)
- Ajout CI Forgejo (deploy FTP via lftp)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/js/onload.js

@@ -27,7 +27,7 @@ function headerShrink() {
 }
 
 function toggleDonationButton() {
-  const btn = document.getElementById('btn--don__mobile');
+  const btn = document.getElementById('donation-cta-mobile');
   const section = document.getElementById('section__donation');
   const footer = document.getElementById('site-footer');
 
@@ -61,7 +61,7 @@ function videos(){
   let section = document.getElementById("section__video");
   console.log(section);
 
-  let videoslinks = document.querySelectorAll(".videos__li");
+  let videoslinks = document.querySelectorAll(".testimony-item");
   videoslinks.forEach(function (video, index) {
 
     video.addEventListener("click", (event) => {