fix: Prevent data loss when connecting to Nextcloud for the first time

- Load existing data from localStorage before switching to Nextcloud
- This prevents existing teas and entries from being overwritten with empty arrays
- When enabling Nextcloud sync, existing local data is preserved and uploaded

Co-authored-by: trevor1969 <trevor1969@users.noreply.github.com>

app.js

@@ -778,6 +778,30 @@ class TeeTracker {
                     return;
                 }
                 
+                // Load existing data from localStorage before switching to Nextcloud
+                // This prevents data loss when connecting to Nextcloud for the first time
+                const existingTeas = localStorage.getItem(STORAGE_KEY_TEAS);
+                const existingEntries = localStorage.getItem(STORAGE_KEY_ENTRIES);
+                
+                if (existingTeas) {
+                    try {
+                        this.teas = JSON.parse(existingTeas).map(tea => ({
+                            ...tea,
+                            organic: tea.organic !== undefined ? tea.organic : false
+                        }));
+                    } catch (error) {
+                        console.error('Error loading existing teas:', error);
+                    }
+                }
+                
+                if (existingEntries) {
+                    try {
+                        this.entries = JSON.parse(existingEntries);
+                    } catch (error) {
+                        console.error('Error loading existing entries:', error);
+                    }
+                }
+                
                 // Save config WITHOUT password for security
                 // Password will be requested each time or stored in sessionStorage
                 const config = { baseUrl: url, username, path };