Fix frontend CSRF, clean reader URLs, and review findings

CSRF / actions:
- List action forms now send both REQUEST_TOKEN (Contao gate) and _token
  (Symfony, validated via isCsrfTokenValid) — mirrors the editor; fixes
  the 400/500 "Ungültiger CSRF-Token" on publish/toggle/duplicate/delete

Public reader / URLs:
- Reader & results read auto_item via Input::get (marks the route param used)
  so clean path URLs /<page>/<alias> no longer 404
- List controller generates path URLs via ['parameters' => '/'.$alias]
- Allow re-participation in the same session after a 60s cooldown

Review fixes:
- Results: merge answer snapshots by questionId+type (no more split cards on
  label edits); seed "Vielleicht" when allowMaybe so screen matches Excel
- Reader: replace generic answer hint with per-option "weiter zu Frage X"
  only when a jump is configured; strip HTML tags from survey description
- PDF: render free-text frequency summary; drop duplicate "Minimum" label
- Drag-sort: bundle SortableJS locally, drop the duplicated inline sort CSS/JS
  from _survey_assets, throttle the backend MutationObserver
- Backend: move hardcoded tl_survey operation labels to TL_LANG (de+en)
- Remove dead code: SurveyEditorVoter, SurveyPermissionService,
  categoryFilter/categorySummary + helpers, orphaned publishSurvey lang key

Reader layout:
- max-width 1000px (other views keep 1400px); back/next buttons fill the
  width as equal, card-sized halves; sort handle icon offset tweak

Docs: update AI_HANDOVER (dual-token CSRF, clean URLs) and README

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

contao/dca/tl_survey.php

@@ -48,14 +48,14 @@ $GLOBALS['TL_DCA']['tl_survey'] = [
         ],
         'operations' => [
             'editheader' => [
-                'label' => ['Umfrage bearbeiten', 'Umfrage bearbeiten'],
+                'label' => &$GLOBALS['TL_LANG']['tl_survey']['editheader'],
                 'href' => 'act=edit',
                 'icon' => 'edit.svg',
                 'primary' => true,
                 'showInHeader' => false,
             ],
             'edit' => [
-                'label' => ['Fragen bearbeiten', 'Fragen der Umfrage bearbeiten'],
+                'label' => &$GLOBALS['TL_LANG']['tl_survey']['edit'],
                 'href' => 'table=tl_survey_content',
                 'icon' => 'children.svg',
                 'primary' => true,
@@ -81,13 +81,13 @@ $GLOBALS['TL_DCA']['tl_survey'] = [
                 'button_callback' => [SurveyDcaListener::class, 'generateDuplicateSurveyButton'],
             ],
             'delete' => [
-                'label' => ['Löschen', 'Eintrag wirklich löschen?'],
+                'label' => &$GLOBALS['TL_LANG']['tl_survey']['delete'],
                 'href' => 'act=delete',
                 'icon' => 'delete.svg',
                 'attributes' => 'onclick="if(!confirm(\'Eintrag wirklich löschen?\'))return false;Backend.getScrollOffset()"',
             ],
             'show' => [
-                'label' => ['Details', 'Details des Elements ID %s anzeigen'],
+                'label' => &$GLOBALS['TL_LANG']['tl_survey']['show'],
                 'href' => 'act=show',
                 'icon' => 'show.svg',
             ],
@@ -148,17 +148,6 @@ $GLOBALS['TL_DCA']['tl_survey'] = [
             'relation' => ['type' => 'hasMany', 'load' => 'lazy', 'table' => 'tl_survey_category', 'field' => 'id'],
             'sql' => 'blob NULL',
         ],
-        'categoryFilter' => [
-            'label' => &$GLOBALS['TL_LANG']['tl_survey']['categoryFilter'],
-            'inputType' => 'select',
-            'options_callback' => [SurveyDcaListener::class, 'getUsedCategoryFilterOptions'],
-            'eval' => ['includeBlankOption' => true, 'chosen' => true, 'findInSet' => true],
-            'sql' => "varchar(255) NOT NULL default ''",
-        ],
-        'categorySummary' => [
-            'label' => &$GLOBALS['TL_LANG']['tl_survey']['categorySummary'],
-            'sql' => 'text NULL',
-        ],
         'published' => [
             'label' => &$GLOBALS['TL_LANG']['tl_survey']['published'],
             'inputType' => 'checkbox',
@@ -253,7 +242,7 @@ if ('cli' !== PHP_SAPI) {
             System::getContainer()->get('database_connection')->fetchFirstColumn('SHOW COLUMNS FROM tl_survey'),
         );
         $hasListMetadataColumns = !array_diff(
-            ['categoryfilter', 'categorysummary', 'templatefilter', 'templatesummary', 'assignedmembersfilter', 'assignedmemberssummary'],
+            ['templatefilter', 'templatesummary', 'assignedmembersfilter', 'assignedmemberssummary'],
             $columnNames,
         );
     } catch (\Throwable) {
@@ -264,8 +253,6 @@ if ('cli' !== PHP_SAPI) {
         $GLOBALS['TL_DCA']['tl_survey']['list']['label']['fields'] = ['title', 'alias'];
 
         unset(
-            $GLOBALS['TL_DCA']['tl_survey']['fields']['categoryFilter'],
-            $GLOBALS['TL_DCA']['tl_survey']['fields']['categorySummary'],
             $GLOBALS['TL_DCA']['tl_survey']['fields']['templateFilter'],
             $GLOBALS['TL_DCA']['tl_survey']['fields']['templateSummary'],
             $GLOBALS['TL_DCA']['tl_survey']['fields']['assignedMembersFilter'],