Refactor HTMX fragment architecture: DRY split into auth endpoints + shared templates

- Created templates/partials/form/_licence.php (shared HTML, no auth logic)
- Created templates/partials/form/_format-website.php (shared HTML, no auth logic)
- Created src/FragmentRenderer.php helper for clean fragment rendering
- Created public/{admin,partage}/fragments/ subdirectories
- Created thin fragment endpoint files: auth guard + data fetch + render template
- Updated all hx-post references in templates to new fragments/ paths
- Updated partage/index.php routing for new fragments subdirectory
- Kept old fragment files as thin delegates for backward compat
- Updated nginx config: added PHP handler in /partage/ location block

nginx/xamxam.conf

@@ -156,6 +156,14 @@ server {
 
     # Share-link (partage) — handled by front controller
     location /partage/ {
+        # Serve PHP fragments directly
+        location ~ \.php$ {
+            include snippets/fastcgi-php.conf;
+            fastcgi_pass unix:/var/run/php/php8.4-fpm.sock;
+            fastcgi_param PHP_VALUE "upload_max_filesize=1024M \n post_max_size=1024M";
+            fastcgi_read_timeout 300;
+            fastcgi_send_timeout 300;
+        }
         try_files $uri /index.php$is_args$args;
     }