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>

src/Service/SurveyFlowService.php

@@ -112,6 +112,29 @@ final class SurveyFlowService
         ];
     }
 
+    /**
+     * Beschreibt das Sprungziel einer Ja/Nein-Antwort über Positionsnummer und Label.
+     *
+     * @return array{position:int,label:string}|null
+     */
+    public function describeJumpTarget(SurveyModel $survey, int $targetQuestionId): ?array
+    {
+        if ($targetQuestionId <= 0) {
+            return null;
+        }
+
+        foreach ($this->getOrderedQuestions($survey) as $index => $question) {
+            if ((int) $question->id === $targetQuestionId) {
+                return [
+                    'position' => $index + 1,
+                    'label' => trim((string) $question->question),
+                ];
+            }
+        }
+
+        return null;
+    }
+
     /**
      * @return list<SurveyContentModel>
      */