fix: fix 500 error on homepage from ZOPK facts query

Replace broken distinct() call with group_by() and add db.rollback()
in except handler to prevent failed transaction from cascading.

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

blueprints/public/routes.py

@@ -133,23 +133,25 @@ def index():
         if current_user.is_authenticated:
             try:
                 from database import ZOPKKnowledgeFact, ZOPKNews
-                from sqlalchemy import distinct
                 # Pobierz najnowszy fakt z każdego z 3 różnych artykułów
-                recent_news_ids = db.query(distinct(ZOPKKnowledgeFact.source_news_id)).join(ZOPKNews).filter(
+                recent_news_ids = db.query(
+                    ZOPKKnowledgeFact.source_news_id
+                ).join(ZOPKNews).filter(
                     ZOPKKnowledgeFact.confidence_score >= 0.5,
                     ZOPKNews.published_at.isnot(None)
+                ).group_by(
+                    ZOPKKnowledgeFact.source_news_id, ZOPKNews.published_at
                 ).order_by(ZOPKNews.published_at.desc()).limit(3).all()
                 news_ids = [r[0] for r in recent_news_ids]
                 if news_ids:
-                    # Po jednym fakcie z każdego artykułu
                     for nid in news_ids:
                         fact = db.query(ZOPKKnowledgeFact).filter(
                             ZOPKKnowledgeFact.source_news_id == nid
-                        ).order_by(ZOPKKnowledgeFact.confidence_score.desc()).first()
+                        ).first()
                         if fact:
                             zopk_facts.append(fact)
             except Exception:
-                pass
+                db.rollback()
 
         # Sprawdź czy użytkownik ma deklarację członkowską w toku
         pending_application = None