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/format-website.php

@@ -0,0 +1,29 @@
+<?php
+/**
+ * Admin fragment: Site web format fieldset (HTMX partial).
+ */
+require_once __DIR__ . '/../../../bootstrap.php';
+require_once __DIR__ . '/../../../src/AdminAuth.php';
+App::boot();
+
+AdminAuth::requireLogin();
+
+require_once APP_ROOT . '/src/FragmentRenderer.php';
+
+$db = Database::getInstance()->getConnection();
+
+$stmt = $db->prepare('SELECT id FROM format_types WHERE name = ? LIMIT 1');
+$stmt->execute(['Site web']);
+$websiteFormatId = $stmt->fetchColumn();
+
+$selectedFormats = isset($_POST['formats']) && is_array($_POST['formats'])
+    ? array_map('intval', $_POST['formats'])
+    : [];
+
+FragmentRenderer::render('form/_format-website', [
+    'fieldsetId'      => 'edit-website-url-fieldset',
+    'selectedFormats' => $selectedFormats,
+    'websiteFormatId' => $websiteFormatId,
+    'websiteUrl'      => $_POST['website_url']   ?? '',
+    'websiteLabel'    => $_POST['website_label'] ?? '',
+]);