feat: hide logout button when admin is not logged in

- Add conditional rendering for "Abmelden" button based on isAdminLoggedIn state
- Button only appears when localStorage contains "isAdminLoggedIn": "true"
- Improves UI cleanliness by hiding unnecessary logout option for regular users
- Maintains existing admin warning banner and logout functionality when needed

CHANGELOG.md

@@ -1,3 +1,25 @@
+## [1.6.670] – 2025-07-31
+
+- feat: implement modal chart system with conditional UI and message filtering
+
+- Add automatic data loading on IsoChartView modal open with timeout to prevent infinite loops
+- Implement conditional UI visibility in IsoChartActionBar using CSS visibility property
+- Create stable layout where controls reserve space when hidden (DatePicker, DIA dropdown, "Daten laden" button)
+- Add Report.tsx component with precise CableLine filtering using exact string matching
+- Enhance message filtering with debug logging and fallback identifier support
+- Integrate chartTitle state management for seamless switching between "Messkurve" and "Meldungen"
+- Add useIsoDataLoader hook for automatic chart data loading without user interaction
+- Implement enhanced filtering logic to prevent false matches (CableLine1 vs CableLine16)
+- Style Report component with consistent table layout matching MeldungenView design
+- Add visual filter indicators and improved error messaging for better UX
+
+Technical improvements:
+- Replace conditional rendering with visibility control to maintain layout stability
+- Add comprehensive logging for debugging message source filtering
+- Implement proper cleanup for timeouts to prevent memory leaks
+- Use exact string matching and prefix validation for precise slot identification
+
+---
 ## [1.6.669] – 2025-07-31
 
 - feat: Meldungen in in Iso Chart