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

app/public/admin/fragments/licence.php

@@ -0,0 +1,23 @@
+<?php
+/**
+ * Admin fragment: licence section (HTMX partial).
+ */
+require_once __DIR__ . '/../../../bootstrap.php';
+require_once __DIR__ . '/../../../src/AdminAuth.php';
+AdminAuth::requireLogin();
+
+require_once APP_ROOT . '/src/Database.php';
+require_once APP_ROOT . '/src/FragmentRenderer.php';
+
+$licenseTypes = Database::getInstance()->getAllLicenseTypes();
+
+FragmentRenderer::render('form/_licence', [
+    'adminMode'       => true,
+    'accessTypeId'    => $_POST['access_type_id'] ?? '',
+    'licenseId'       => $_POST['license_id']     ?? '',
+    'licenseCustom'   => $_POST['license_custom'] ?? '',
+    'cc2r'            => !empty($_POST['cc2r']),
+    'wantLicense'     => !empty($_POST['want_license']),
+    'hxPost'          => '/admin/fragments/licence.php',
+    'licenseTypes'    => $licenseTypes,
+]);