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>

thanks/index.html

@@ -78,27 +78,27 @@
     </header>
 
     <main>
-      <p class="p__baseline-big">
+      <p class="hero-heading">
         Thank you!
       </p>
 
-      <p class="p__baseline">
+      <p class="subheading">
         Your support allows us to continue investigating with complete independence.</p>
 
-        <p class="p__baseline">We sincerely thank you for your solidarity, which is essential to the pursuit of our&nbsp;mission.</p>
+        <p class="subheading">We sincerely thank you for your solidarity, which is essential to the pursuit of our&nbsp;mission.</p>
         
-        <p class="p__baseline"><a href="https://www.index.ngo/en/">Back to home page →</a></p>
+        <p class="subheading"><a href="https://www.index.ngo/en/">Back to home page →</a></p>
       </p>
     </main>
 
     <footer id="site-footer">
-      <div class="site-footer__container">
+      <div class="footer-container">
    
 
       
 
-        <div class="footer__mentions">
-          <p class="p__small">
+        <div class="footer-mentions">
+          <p class="text-small">
             © 2025  Index Investigation | <a target="_blank" href="https://www.index.ngo/mentions-legales/">Mentions légales</a>  
           </p>
         </div>