add form help blocks: DB table, admin editor, live rendering in partage form

app/templates/partials/form/form-help-block.php

@@ -0,0 +1,26 @@
+<?php
+/**
+ * Renders a single form help block as HTML.
+ *
+ * Variables consumed:
+ *   string $helpContent — raw Markdown string from the DB (may be empty).
+ *
+ * Outputs nothing when $helpContent is empty or whitespace-only.
+ * Parsedown must already be autoloaded (it is, via bootstrap → APP_ROOT/src/).
+ */
+
+$helpContent = trim($helpContent ?? '');
+if ($helpContent === '') {
+    return;
+}
+
+require_once APP_ROOT . '/src/Parsedown.php';
+$pd   = new Parsedown();
+$pd->setSafeMode(true);
+$html = $pd->text($helpContent);
+?>
+<div class="form-help-block">
+    <?= $html ?>
+</div>
+<?php
+unset($helpContent, $pd, $html);