fix(sync): Add WiFi-only check for onSave and background sync

- SyncWorker: Add central WiFi-only guard before all sync operations
- NoteEditorViewModel: Add WiFi-only check before onSave sync trigger
- Prevents notes from syncing over 5G/mobile when WiFi-only is enabled
- Fixes: onSave sync ignored WiFi-only setting completely

android/app/src/main/java/dev/dettmer/simplenotes/sync/SyncWorker.kt

@@ -9,6 +9,7 @@ import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import androidx.work.CoroutineWorker
 import androidx.work.WorkerParameters
 import dev.dettmer.simplenotes.BuildConfig
+import dev.dettmer.simplenotes.utils.Constants
 import dev.dettmer.simplenotes.utils.Logger
 import dev.dettmer.simplenotes.utils.NotificationHelper
 import kotlinx.coroutines.CancellationException
@@ -88,6 +89,32 @@ class SyncWorker(
                 return@withContext Result.success()
             }
             
+            if (BuildConfig.DEBUG) {
+                Logger.d(TAG, "📍 Step 2.5: Checking WiFi-only setting")
+            }
+            
+            // 🆕 v1.7.0: WiFi-Only Check (zentral für alle Sync-Arten)
+            val prefs = applicationContext.getSharedPreferences(
+                Constants.PREFS_NAME,
+                Context.MODE_PRIVATE
+            )
+            val wifiOnlySync = prefs.getBoolean(
+                Constants.KEY_WIFI_ONLY_SYNC,
+                Constants.DEFAULT_WIFI_ONLY_SYNC
+            )
+            
+            if (wifiOnlySync && !syncService.isOnWiFi()) {
+                Logger.d(TAG, "⏭️ WiFi-only mode enabled, but not on WiFi - skipping sync")
+                Logger.d(TAG, "   User can still manually sync when on WiFi")
+                
+                if (BuildConfig.DEBUG) {
+                    Logger.d(TAG, "✅ SyncWorker.doWork() SUCCESS (WiFi-only skip)")
+                    Logger.d(TAG, "═══════════════════════════════════════")
+                }
+                
+                return@withContext Result.success()
+            }
+            
             if (BuildConfig.DEBUG) {
                 Logger.d(TAG, "📍 Step 3: Checking server reachability (Pre-Check)")
             }

android/app/src/main/java/dev/dettmer/simplenotes/ui/editor/NoteEditorViewModel.kt

@@ -372,6 +372,16 @@ class NoteEditorViewModel(
             return
         }
         
+        // 🆕 v1.7.0: WiFi-Only Check
+        val wifiOnlySync = prefs.getBoolean(Constants.KEY_WIFI_ONLY_SYNC, Constants.DEFAULT_WIFI_ONLY_SYNC)
+        if (wifiOnlySync) {
+            val syncService = WebDavSyncService(getApplication())
+            if (!syncService.isOnWiFi()) {
+                Logger.d(TAG, "⏭️ onSave sync blocked: WiFi-only mode, not on WiFi")
+                return
+            }
+        }
+        
         // Check 3: Throttling (5 seconds) to prevent spam
         val lastOnSaveSyncTime = prefs.getLong(Constants.PREF_LAST_ON_SAVE_SYNC_TIME, 0)
         val now = System.currentTimeMillis()