fix: 8 quality + UX improvements

1. Cookie 'Zwecke' false positive: added 'um...zu', 'dienen', 'helfen',
   'ermöglichen' patterns — catches purpose descriptions without 'Zweck'
2. Kurzhinweis: added empty all_checks for short documents (<200 words)
3. Bezeichnungsfeld: placeholder shows 'Version / Stand' for typed docs,
   'Dokumentname' for 'Sonstiges'
4. DocCheckTab state persistence: entries + results survive navigation
5. DocCheck history: saves each check with date, doc count, findings
6. History display: 'Letzte Pruefungen' section at bottom of tab
7. ChecklistView: shows 'X von Y Pruefpunkten bestanden' per document
8. Results persist in localStorage across page navigation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/services/dsi_document_checker.py

@@ -184,7 +184,10 @@ COOKIE_CHECKLIST = [
     {"id": "cookie_types", "label": "Arten der Cookies",
      "patterns": [r"(?:notwendig|essentiell|funktional|statistik|marketing|tracking)", r"cookie.*(?:art|typ|kategori)"]},
     {"id": "purposes", "label": "Zwecke der Cookies",
-     "patterns": [r"zweck.*cookie", r"cookie.*zweck", r"(?:wofuer|wozu|warum).*cookie"]},
+     "patterns": [r"zweck.*cookie", r"cookie.*zweck", r"(?:wofuer|wozu|warum).*cookie",
+                  r"cookies?\s+(?:ein|ver)?\s*,?\s*um\s+", r"(?:setzen|verwenden|nutzen)\s+.*cookies?\s+.*(?:um|fuer|für)",
+                  r"(?:analyse|marketing|tracking|funktional)\w*\s*cookies?\s*\.?\s*(?:um|damit|diese|sie)",
+                  r"cookies?\s+(?:dienen|helfen|ermöglichen|ermoeglichen)"]},
     {"id": "retention", "label": "Speicherdauer der Cookies",
      "patterns": [r"(?:speicherdauer|laufzeit|gueltigk|ablauf).*cookie", r"cookie.*(?:\d+\s+(?:tag|monat|jahr)|session)"]},
     {"id": "third_party", "label": "Drittanbieter-Cookies",
@@ -232,6 +235,7 @@ def check_document_completeness(
             "doc_title": doc_title,
             "doc_url": doc_url,
             "doc_type": doc_type,
+            "all_checks": [],  # No checks run for short documents
         })
         return findings