fix: improve tipping user journey

- Dashboard "Jetzt tippen" opens TipModal directly instead of
  navigating to /spiele (no more dead-end spielplan)
- After tipping, dashboard updates to show "Dein Tipp: X:Y ✓"
- Spielplan auto-opens all sections when only 1-2 exist
  (no more collapsed "Demnächst" as only section)

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

frontend/src/pages/MatchesPage.tsx

@@ -81,7 +81,12 @@ export default function MatchesPage() {
     if (allMatches.length > 0) {
       const filteredMatches = allMatches.filter(m => !stageFilter || m.stage === stageFilter);
       const sections = groupIntoSections(filteredMatches);
-      setOpenSections(new Set(sections.filter(s => s.defaultOpen).map(s => s.key)));
+      // If only 1-2 sections exist, open all of them
+      if (sections.length <= 2) {
+        setOpenSections(new Set(sections.map(s => s.key)));
+      } else {
+        setOpenSections(new Set(sections.filter(s => s.defaultOpen).map(s => s.key)));
+      }
     }
   }, [allMatches]); // only on initial load