fe_comment: recipients are the FE users of the feedback group

- The selectable recipients are no longer a hand-maintained setting but
  every active frontend user of the feedback group (feUserGroup) with a
  valid e-mail address; the id is the fe_users uid, so a stored selection
  survives users joining or leaving. The `recipients` setting is marked
  unused
- Each recipient in the state payload carries label, email and selected
  (the stored choice), for a checkbox list with "select all" above the
  submit button
- submit accepts the checked ids directly ({"recipients": [uids]}),
  validates them against the group, stores and uses them, and reports
  the addresses used as sentTo; no selection falls back to mailTo
- migrations/check_fecomment_user.php: all summaries and items of one
  user incl. deleted ones, for diagnosis

packages/fe_comment/Classes/Service/FeedbackState.php

@@ -76,7 +76,7 @@ final class FeedbackState
         return [
             'allowed' => true,
             'user' => ['name' => $user['name'], 'email' => $user['email']],
-            'recipients' => $this->recipientOptions(),
+            'recipients' => $this->recipientOptions($summaryPayload['recipients'] ?? []),
             'overviewUrl' => $this->overviewUrl(),
             'summary' => $summaryPayload,
             // the submit button may be active (the endpoint rejects an empty summary)
@@ -91,7 +91,7 @@ final class FeedbackState
      * bodies except `upload` (multipart: file + feedback).
      */
     private const ACTIONS = [
-        'submit' => ['method' => 'POST', 'url' => '/api/fe-comment/submit'],
+        'submit' => ['method' => 'POST', 'url' => '/api/fe-comment/submit', 'body' => ['recipients' => 'int[] (optional, the checked recipient ids)']],
         'updateSummary' => ['method' => 'POST', 'url' => '/api/fe-comment/summary', 'body' => ['generalNotes' => 'html', 'recipients' => 'int[]']],
         'createItem' => ['method' => 'POST', 'url' => '/api/fe-comment/feedback', 'body' => ['url' => 'string', 'note' => 'html']],
         'updateItem' => ['method' => 'POST', 'url' => '/api/fe-comment/feedback/{uid}', 'body' => ['url' => 'string', 'note' => 'html']],
@@ -168,12 +168,63 @@ final class FeedbackState
         ], $rows);
     }
 
-    /** @return array<int,array{id:int,label:string}> */
-    private function recipientOptions(): array
+    /**
+     * Who a summary can be sent to: every active FE user of the feedback
+     * group (extension setting feUserGroup) with an e-mail address - the
+     * same group that may use the tool (decision Olli 2026-10-09). Keyed by
+     * fe_users uid, which doubles as the id the front end sends back, so a
+     * selection stays valid while users join or leave. Group 0 = nobody
+     * (never all frontend users).
+     *
+     * @return array<int,array{label:string,email:string}> fe_users uid => recipient
+     */
+    public function recipientMap(): array
+    {
+        $group = $this->settings->feUserGroup();
+        if ($group <= 0) {
+            return [];
+        }
+        $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('fe_users');
+        $rows = $queryBuilder->select('uid', 'username', 'name', 'email')->from('fe_users')
+            ->where(
+                $queryBuilder->expr()->inSet('usergroup', (string)$group),
+                $queryBuilder->expr()->neq('email', $queryBuilder->createNamedParameter(''))
+            )
+            ->orderBy('name')->addOrderBy('username')
+            ->executeQuery()->fetchAllAssociative();
+        $map = [];
+        foreach ($rows as $row) {
+            $email = trim((string)$row['email']);
+            if (!GeneralUtility::validEmail($email)) {
+                continue;
+            }
+            $map[(int)$row['uid']] = [
+                'label' => trim((string)$row['name']) ?: (string)$row['username'],
+                'email' => $email,
+            ];
+        }
+        return $map;
+    }
+
+    /**
+     * The recipients for the checkbox list above the submit button.
+     * `selected` mirrors the summary's stored choice, so checkboxes survive
+     * a reload. Addresses are shown on purpose: only logged-in members of
+     * the feedback group ever see this payload.
+     *
+     * @param int[] $selectedIds
+     * @return array<int,array{id:int,label:string,email:string,selected:bool}>
+     */
+    private function recipientOptions(array $selectedIds): array
     {
         $options = [];
-        foreach ($this->settings->recipients() as $id => $recipient) {
-            $options[] = ['id' => $id, 'label' => $recipient['label']];
+        foreach ($this->recipientMap() as $id => $recipient) {
+            $options[] = [
+                'id' => $id,
+                'label' => $recipient['label'],
+                'email' => $recipient['email'],
+                'selected' => in_array($id, $selectedIds, true),
+            ];
         }
         return $options;
     }